Spotting for 4 days after sex, 3 days after period.

Hey all! I have a scheduled dr.s appt for Thursday to address this issue, however, Thursday is a long time away for me, and I just need to soothe my anxiety. Ok, so here's my issue...

About 4 weeks ago my boyfriend and I were having sex, at which point I got the most horrible cramp and had to make him stop. I felt sick, got a cold chill and started sweating, then had a bowel movement and felt entirely better. 2 days later, when I went to the bathroom and wiped I noticed black blood on my tissue, the next day it was light brown, and then after that there was nothing. A week and a half later I started my period. It was normal as usual, lasted for almost a full 7days. 2 days after my period went off, my boyfriend and I had sex again, a little on the rough side, but not nearly as rough as usual. After sex, I went to the bathroom to clean up and everything was normal. The next morning however, when I wiped there was light brown blood on the tissue, and its been like that for the past 4 days. Around the 2nd day of this strange spotting I started noticing that my breasts were very tender.

I highly doubt I'm pregnant, as we are hypervigilant about using protection and as far as I know there were no malfunctions with the condom use. No, I am not on any form of birth control.

Has anyone else experienced this, and if so, when you went to the doctor was everything fine? I'm such a freak about my health, that I've gotten myself terrified of all the possibilities it could be.