Why stomachache is happening. It.

I had first time sex with protection on 5th May timing between 1:00pm to 2:pm. My partner said it was safely done.. but I have doubt. So I took unwanted pill just I don't want to need any kind of pregnancy.6th may (1:30 -to 2:00pm).while doing intercourse we found condom some times slipped.. but I don't know it's true or not.so just because I thought so I took that pill.. but after sex I feel burning in my vagina.. and after 2-3 days cramp started in my stomach.and still having pain.feeling irritated due to stomachache. One more thing it was my first intercourse .so I m but more concern about it.. because I always feel stomachache.is tis pregnancy o any kind of other problem.today I feel menstrual pain in my vagina but menstruation is not happening.. just having pain.. i dojt understand the pain type.. I m unmarried. So I m in tension.. am i pregnant?plz help.. how do I recognise it .