I have bad cramping and tightness of my uterus after intercourse. It makes hubby feel horrible, but it's not that painful. It's only painful when I can feel my skin stretching from how big i'm getting. I'm 14 weeks along.
Unless your doctor has told you otherwise, it's fine. Be warned though. It's not uncommon to spot and/or cramp afterwords though, so if you so, it could be from that.