There are a few possibilities. If you are sexually active without any protection, pregnancy
should be contemplated. Please get an assessment of the serum beta-hCG
to confirm/exclude pregnancy and plan further management if positive. If negative, you should get assessed for hormone imbalances through investigation. A trans-vaginal sonogram also will help assess the state of the pelvic organs. You may need a course or two of hormones to help recover the normal cycles. Hope this helps.