post baby bleeding after sex

So I completely stopped bleeding and we decided to try and have sex. I had been feeling great and everything even a little frisky. Well I know that if I did major walking or house work I tended to bleed alittle. Well after not bleeding and taking it easy I figured we could give it a try. I told him we would stop at any pain or whatever. Well not even 2 minutes into it I told him to stop because I wanted him to check for bleeding. Come to find out their was a lot. I've had a rough recovery after my labor/c section. I spent 80 hours in labor only to end up with a c section. I wish they would have done it sooner. my little man was wedged in my pelvis and never would have been able to deliver vaginaly. Anyways I was wondering if it's common to have bleeding after sex when you first start back up. I'm sure I probably was the one to cause it as I am only 4 weeks pp. ya ya I know but I've been feeling very frisky at time and it just happened.