Weight and Fertility

I have had no periods for four years but am otherwise healthy. I have had scans on my ovaries that are normal, and three blood tests suggesting that my hormones are in normal range.

The endocrine faculty at the hospital believe that my lack of periods is due to being underweight by half a stone. However I have always been very slim, other than a short spell at university.

My periods stopped when I stopped taking the pill, at my heaviest weight, and in the last four years I have only had three periods in total. I have had a lot of stress over the years and believe this to be the main cause of my problems, rather than my weight.

My doctor and the hospital are pushing me to start taking the pill again, but I don't think this will help the probelem, just cover it up. I did agree to take some progesterone on two occasions for a week at a time, but even on the highest dose nothing happened. It only made me feel very anxious.

I am concerend that no periods for such a long time will impact on my fertility. I am 29 years old and would very much like to have children.

Does a lack of periods mean you cant get pregnant? How can I kick start menstruation? I have tried nutritional means but is there a more drastic approach?