hi im 19 and iv been having problem with my period as previously my period had stopped for 3 months and were back on again as normal and know im having the same problem as its been a month that im not having my periods im scared that me and my partner got sexually active but we did not have sexual intercourse and after 7 days of that i had my period, but the next month my periods stopped so i wanted to know what might be causing this problem.