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
. 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.