Until december of last year i had regular periods but this year i have only got my period in march & april.went to doctor &not pregnant what can it be?

Anovulation?: If you aren't pregnant, Anovulation is one of the more common reasons for missing periods. There are many things that can causes you not to ovulate. Thyroid problems, PCOS, obesity, stress, training for a marathon, medication, chronic illnesses.... If it is a persistent problem, you should be tested to find out why. Best wishes!