Hey, My Boyfriend And I Have Vigorous Sex About 3-4

Hey, my boyfriend and I have vigorous sex about 3-4 times a week, but nothing involving actual damage to his penis. He said the other day after he urinated there was a small dot of blood that came onto his tissue when he dried his penis. It wouldn't be an STD because we are both completely faithful to one another. And sometimes after sex he says his penis is a bit sore/sensitive. He doesn't think it's something to worry about but I am a little worried. What could be the cause? Thank you.