why does my bf (18) experience a numb penis during intercourse?

My boyfriend and I have some rather rough sex, sometimes he struggles to ejaculate. He often says that it felt like he had finished but nothing had come out and other times he struggles even getting close because he claims his penis feels numb. I’m wondering if this is a result of the rough sex or if he’s just not into it and is too kind to tell me… I sometimes feel pain from the sex too which leads me to believe that we may just have to chill out on how rough we are but once you start it’s hard to go back yk… so any advice would be helpful!