It is unlikely that you got pregnant from that encounter. If you want to find out, the best way would be to test for pregnancy about 14 days after the encounter. I would test one more time about a week after that to confirm.
By the way, you should see your doctor about your irregular periods, and perhaps some birth control.
Good luck!
Dr B
U could have a cyst on ur overies that happened to me and I didnt get my period for 3 months