😩heavy bleeding during sex😳??

Ok Ladies, help me...!
I'm an adult with 2 children an I have never experienced this before. 
   So I been dealing with this guy an we are sexually active,some what frequent now. So here is the thing he is COMPLETELY HUGE🍆 I mean maybe 10inches an extremely thick😏,
I haven't had any sexual contact before him in about 5months,so anyway long story Short I barley got off my cycle 2weeks ago and we had a very short session but when we was done it was a lot of blood, but here's the thing we had sex the night before an it didn't happen!! 
So what can be the reason for me to flow? And I'm still flowing 😩🤔