I have been told many horror stories about women coming off the pill and waiting months and months for a period. Doctors say it's safe, but not having a period for six months seems pretty worrying to me. What do you think?

There is no evidence that taking the pill, even for long periods, will harm a woman's underlying system for producing monthly periods. After stopping the pill, most women start their periods again within three months. If you haven't after six months, there are two main possibilities: you are pregnant, or your ovaries have ceased to work. This could have several causes, from early menopause to problems with your pituitary and ovarian hormone-producing or feedback systems. A gynaecological endocrinologist will sort that out. If that is the case, it would almost certainly have happened regardless of whether or not you took the pill.

Does breathing through your mouth make you more susceptible to infection? I seem to have constant colds and blocked noses, and wonder whether this may be why.

It's more likely that your susceptibility to infection or allergy in your nose is making you breathe through your mouth. Constant colds and a blocked nose suggest chronic allergic rhinitis (like hay fever, but year round). The alternative is chronic sinusitis, in which your sinuses are constantly infected. For the first you may need anti-allergy treatment, for the second antibiotics and perhaps sinus washouts. Your GP will point you in the right direction.

· Do you have a question for Dr Smith? Email doctordoctor@theguardian.com