Okay Doc, On April 5th I Had Sex For The

okay doc, on April 5th I had sex for the first time and we done it unsafe, but he did not ejaculate just had pre-cum. 6-7 days after that I got my period that lasted about 4-5 days. but my periods have always been irregular. but, like a week after I done it, I got put on birth control for acne I took them for about a month then stopped. now it is May, 28th and I still don't have my period. what are the chances of me being pregnant? my lower stomach has been crampy but I was thinking it was my period coming cause I have headaches and bloating also! just like my period does every time it's about to come. what's the chances of me being pregnant? (also, when we done it, it was for about 10 seconds then we stopped and like 10 minutes later done it again for like 10 seconds. and we were both virgins)