stomach problems help!

I'm on birth control and suppose to get my period on Tuesday of this week. I have had sex with my boyfriend and everytime he does cum in me. for the past 2 weeks I been feeling really bloated and stomach hurts and feel uncomfortable and sometimes I feel like throwing up at weird times and also I been seeing a tiny tiny blood when I pee and after we have sec, which doesn't usually happen at all but the past 2 times this week we had sex since 2 weeks ago it happened... does anyone know what this is ? I took a pregnancy test the other day and it was negative but being 2 weeks pregnant iidk if it would show up on a test.. help! :(