What Causes Irregularities In Menstruation?

Hiii, I m having intercouse for few min from last 6 months BT then to I have ipil....in d month of may I had intercouse just for 1 min BT there was no ejaculation done and after that I even got ma periods in June and after that I never had sex BT nw I m nt getting ma periods my date was 12july ....plzzz sujest something ....