I’m having periods that are usually two or three months apart and my doctor says it’s because I’m doing too much exercise. I’m 19, healthy, and studying to be a medical office assistant, I walk, run or kick-box every day but feel good when I do it and not good when I don’t. I’m slim (I think my body mass index is 18) but I feel good energy at this weight. I’m never sick, I eat well, don’t smoke and really try to be healthy. Do you think that too much exercise is causing my infrequent periods?