I have been on the depo shot for two years and I have never had a period untill two months ago. The only thing that has changed is now I am taking a weight loss pill perscribes by my doctor. Is the pill messing with the shot? Does it make the shot less affective? Could I be pregnant? Please someone help me because me and my fiancé have a two year old and we are very active and we don't use any form of protection.