What Causes Brown Spotting After Having Unsafe Sex?

I doctor I have a question that's really important. Im not sure if I'm pregnant or not because my boyfriend and I had unportected sex and like two weeks ago and yesterday I started spotting brown then a few hours later it was like I had my period red blood started coming out but I don't know if I'm on my period because its to early and I'm having cramps on one side and it doesn't go away so I don't know what's wrong