Need help

I have a doctors appointment already for this..... I’m two months postpartum. I decided to have sex at 4 weeks postpartum because I had stopped bleeding and was feeling fine. I didn’t tear so I didn’t need any stitches. I didn’t have a problem with having sex until recently. So recently while having sex it’s painful and I start to bleed heavily, to the point where I get dizzy. It stops after a while maybe like 2 hours of heavy bleeding. I just wanted to know if this has happened to any one or if anyone can tell me why it’s happening. I have had 2regular periods since giving birth