I need advice!!!

Me and my SO we're having sex and he decided he wanted to do doggy so I was like okay cause we have done it before.

Well I was very sensitive to deep penetration and it hurt which is strange because I only get that way when I'm on or about to start my period. I'm on birth control and haven't missed a day and taken it on time like I have every other day.

At the end I bleed. What should I do?