I'm scared kinda!

Basically, my boyfriend and I had unprotected sex 3 weeks ago. He never came in me then after that two weeks later I got my period but it only lasted two day so I'm not sure if that was a period. Because I'm usually last up to 5 days. Now, every since that I've been feeling bloated from the lower part of my stomach and I'm not sure what is. I took two pregnancy test and they said I wasn't pregnant. It's just I'm not sure and I think I'm just being paranoid for no reason.