I'm 19 and 2 and a half weeks ago, my boyfriend and I were making out and it went a little far. He went in (1-2 inches) but not all the way. I'm not sure whether he had pre-ejaculated prior to going in. Because my period is somewhat irregular, I couldn't tell whether I had been ovulating or was in my ovulation period during that time. My last period was around the 25th of December and ended on the 1st of January. My period is suppose to come within these couple of days but it shows no signs of coming. We have taken two pregnancy tests. One on the 24th or 25th and then another one on the 28th. Both tested negative. Should I be worried?