Hi, The possibilities are hormonal imbalance as often happens when there are sudden weight changes, stress, infection or use of certain medications, and if you are sexually active without any contraception, pregnancy. Please get a blood test to exclude/confirm pregnancy and once pregnancy is ruled out, get properly investigated to look for other causes through a physical exam by a specialist, blood counts and urinalysis along with a trans-vaginal sonogram. Hope you find this information useful. Take care.