Sex made me start my period? TMI!!!

So, last night (7-28) DH and I had some really good sex. I was on top, it was very enjoyable. He was pounding hard. And I was riding hard as well. I recently got a Positive OPK on the 26&27. However, this morning I went to pee at work and I’m bleeding. I do feel some pressure on my uterus, but not period cramps per say, more like the pressure from him going in so deep and hard. It’s bright red blood, no vaginal pain, or anything like that. Is this my period? Or blood from rough sex? Or too early to tell, wait and ride it out and see how long it lasts and with what symptoms. This has never happened so I’m kind of unsure if it’s my period or cervical bleeding. Any help is greatly appreciated!