So I had sex with my boyfriend on May 2nd, it was protected (he used a condom and it was my first time having sex)

On may 14th (right around when I was supposed to get my period) I got spotting, light pinkish, then the following day my flow was regular and heavy, then the following day it was spotting and stayed like that for the next 2-3-4 days. I was so stressed about this irregular period the whole time and  that I decided to take a pregnancy test at my schools health clinic on may 21st, a week after the irregular period.

 It was a very clear NEGATIVE, I was obviously relived..

Now it's May 27th and I'm still having abdominal pains and I'm freaking out again because I'm wondering maybe it's a false negative. I could be still ovulating of course, but i'm still worried. 

Any opinions on why i'm still having abdominal pains. I have been eating out a lot more since I started dating my boyfriend, we always go out to eat when we are together. Could that be why I have bad stomach pains? Or maybe stress and anxiety over this? Just want opinions...