Had Unprotected Sex. Took Plan B Later. Had Periods. Feel Nausea, Having Slight Cramps And Green Veins On Breasts. Pregnant?

I had sex for the very first time May 18, 2013. I made a very dumb decision & it was unprotected, we only had sex for 1-3 minutes he didn't finish in me but earlier we were fooling around and he came a couple of times. I took plan b 12-14 hours later just in case and I got my period exactly a week after I took it, which was around the scheduled time. I don't track ovulation since I don't plan on having kids ANY time soon, but I used an online calculator and I should have been ovulating a week prior to having sex so that slims down my chances of getting pregnant. I had a normal 4 day long heavy period on May 25-28 with clots (which is normal for me), and now about 14 days later from the first day of that period I feel like I'm ovulating but since pregnancy symptoms are similar to ovulation symptoms, I took a pregnancy test since it was 3 weeks prior to having sex, which came out negative. I feel nauseas, having slight cramps, green veins on breasts (not sure if they were that prominant before) constipation & I can't really eat...I'm not sure if I'm imagining these things because I'm nervous or is there a possibility that I'm pregnant? I'm going to take another test in a week. PLEASE help!