I have a health problem, if anyone can help me, please do!?

I'm NOT on birth control, I have never been sexually active, and I have skipped my period this month and month before last. I usually get my period either the 2nd or 3rd week of the month. I skipped in April and this month. Can someone help me? I am not obese, i haven't had any significant weight loss or gain, i exercise every Tuesday, Thursday, and sometimes on weekends, I have a healthy, balanced diet, I don't smoke, I have no medications that I take daily, I do not drink any alcoholic beverages, I don't have increased stress, and I don't think I have any cysts because I would be in severe pain. I am only 16 so my skipping is not from age. Please help me.