It is three o'clock in the morning and I am standing in my bathroom, hanging on to the sink with one hand and holding a glass with the other. The cold water babbles out of the tap and into the plughole. I do not want to hear this sound. All I want is to be asleep. Instead I fill the glass, pop two prescription painkillers out of their little foil hammocks and into my mouth, and stare at myself in the mirror. The hyperactive, busy working mother of three has vanished and in her place is a wan, sick, tiny person on a long, non-negotiable journey to the very gates of hell. The only crumb of comfort is the possibility that the return ticket will be valid, if I can just keep going and navigate my way through a beckoning labyrinth of healthcare services and months of long, lonely nights, all of which I must face alone.

Working out why I'm in this predicament is not difficult. There must be thousands like me, people whose relationships have, for one reason or another, ended and who then fall ill.

My partner and I separated amicably seven years ago after 22 years together and I moved into a little house on my own, my two boys by then both at university. My daughter from my first marriage lives 60 miles from my home in Ilkley, West Yorkshire, and is absorbed by a growing family of her own. My oldest son is now four hours away in London and has a brilliant but demanding job. The youngest is a loveable law unto himself in the manner of many young men on a mission to build a career and have fun in equal measure. Before I got ill I thoroughly enjoyed my single life and the sense of coming home to an empty house and being accountable to no one. So it honestly never occurred to me that the party might one day end without my full permission. Sometimes I wonder if, by sheer force of will, I might throw off this sickness and cheat myself back to health as an act of characteristic defiance. After all, just a year ago I was enjoying a brand new job. I was making things happen, having it all, burning the candle at both ends. Grabbing life and living it to the max. My days were rammed with friends, dinners, bars, parties, occasional romance and travel, all rooted in a family that also included three little grandchildren, a friendly former partner and a devoted sister and parents.

But then, audacious and uninvited, my slumbering Crohn's disease muscled its way back into my life after 10 years of good behaviour and exploded inside my body like a comedy firecracker going off. My busy schedule was sucked away unceremoniously, the button on the celestial laptop inadvertently pressed to sleep and the screen suddenly blank and deafeningly quiet.

That's what it feels like, being single and ill. It's very, very quiet. Because in place of the lively interactions that have previously filled the 10 hours-plus of your working day and the lovely warm bath of your chill-out weekends, you are lying on a sofa in an empty house wondering quite what has hit you. Instead of designing and defining your every waking moment, you are at the mercy of a monstrous new master, your psyche lurking powerless inside a body hijacked by disease. Instead of calling your mates and fixing drinks and excursions, you are dreading the ring of the phone because if they ask how you are you'll have to say not good. And who's going to want to hear that, month after month?

Friends do want to hear, of course. And they want to help. But they know this is a battle that, ultimately, you have to fight alone unless you have that all-important partnership contract in your back pocket. Because, like it or not, a partner is the only person who is basically obliged (whether by matrimonial or common-law agreement) to be there for you. And if, like me and thousands of others, you've been a fiercely independent singleton, it's almost unimaginably difficult to suddenly be asking friends for help to do the most basic things like shopping, cooking, vacuuming the stairs, cleaning the loo and even getting dressed.

So you find yourself endlessly doing stuff you don't want to do; tolerating the almost intolerable with no witness to your pain, no warm body to curl up with, no calming hand to soothe you. You hear bad news from the doctor alone because you don't want to subject your mates to hearing the unsavoury medical facts. You sink to your knees half way up the stairs because you can't make it to bed unaided and don't want to trouble anyone to come round and help you into your nightie after News at Ten. A fluffy hot-water bottle becomes your greatest comfort, the nearest thing to a living, breathing human being you can lay your hands on. You chart the long nights by tracking the slow movement of light through your curtains, from sunset to street lamp to sunrise. And the silence of your empty house is deafening.

Suddenly the streets are full of kind people pushing their partners along in wheelchairs. Who the hell is going to push my wheelchair one day if it comes to that? And an even worse thought somehow: whose wheelchair am I going to be able to push, being needed by a loved one grown old?

I've spent plenty of time in hospital over the last six months, watching loyal husbands bringing toilet-bags in and taking washing home, dimly aware that I can't take the same for granted. In hospital, though, we are all alone at night. We all lie there hearing muffled voices, wondering who has rung the alarm button, counting the minutes until the next dose of painkillers is due. We rearrange our drips and tend to our scars and sores alone. But only those with partners can expect to see the same face by the bedside every waking day.

That's what's hardest of all when you're single. You don't have the right to expect someone to rub your back on demand, to go into battle with doctors on your behalf, to just sort of know, day and night, what it feels like – because that's part of their job description.

Put simply, when you're single the unspoken empathy between you and a partner is missing, its absence more inexplicably painful than you could ever confess to your endlessly loving and caring friends.

Without those friends I could not have kept going. My children reacted in different ways from zero to hero – I think they were frightened to see their normally indestructible mother cut down by some weird sort of higher power. You'll be fine, they kept saying. But I wasn't fine. My gut was constricted so that food wasn't passing through properly, my colon horribly ulcerated, my whole body one great big battleground of infection. Everything I ate led to intense pain that lasted for hours at a time. I was often unable to leave the house. A doctor friend rather hilariously described my digestive tract as "rotting".

I didn't want my kids to know the full gory details. So it was friends who provided a human bridge from despair to hope, over which I have gratefully crawled time and again in the last few months. The loving kindness and practical support of my women friends in particular has been awesome. Each time I've been in hospital (five times, two emergency admissions, four operations) they have rallied round, providing food, books, magazines, company, entertainment, love, patience, encouragement, strategy and medical insights. I thank them all. Likewise my sister Sarah, who, despite being 200 miles away and having primary responsibility for our two frail parents, provided herculean quantities of emotional and practical support.

Some of the blokes were great too. And my ex, Ali, who twigged the severity of the situation a couple of months in and took me out in his car on Sundays like an old lady on day release from the care home. And who sometimes just sat watching telly with me and saying little, which was exactly what he would have done had we still been together. It's hard to explain how much that comforted me, like a glimpse of normality in my topsy-turvy new world of illness.

So I'm lucky, and now I'm getting better too. I had to give up my job and haven't worked for months, but I'm learning not to worry and to put health first. This week I started running again, albeit tentatively and at a snail's pace. People say I'm looking better. I'm feeling better too. The new drug infusion therapy is finally kicking in and I've put on 12lbs from my low point of seven stones. And the almost daily calls from my oldest son, full of love and kindness, have comforted and restored me more than I can ever say.

All I've got to do now is shake off this troublesome "sick single woman" persona and remember who and where the healthy me is and reacquaint myself with her as quickly as I can. Then I can get back to having fun being single again. I can't exactly say that the "sickness and health" clause is worth staying in a shaky relationship for, but it's certainly started to look a wee bit more like a close run thing.