after sex issues

I just begin having sex 2 months ago with my boyfriend and we’ve been using protection but it seems like maybe 2 or 3 days after having (rough) sex I’ll get a brownish pinkish discharge, I’m free of infections and uti’s because I went to my clinic 1 month ago but this happens every time we have sex what should I do? Also I do know that if you have rough sex that you can bleed afterwards but does anyone know why I bleed days later?