What Causes Sickness, Vaginal Bleeding With Pain After Unprotected Intercourse?

Hello,
I had unprotected sex for 4 days, and this monday i start feeling sick at the end of monday i start bleeding, I couldn't eat anything and etc. I had my period 2 weeks in half before I had sex. I took pregnancy test it shows me that im not pregnant but few people telling me that I might be pregnant. Is there a chance that im pregnant or its just a regular pain after sex?