I had a very similair experience. I was bleeding almost everytime after sex ( I'm not a virgin). It wasn't painful the next day but it did make me nervous. Also, there was a large laceration right near the vaginal opening. I visited the OBGYN and she said that it was bc of tearing. She mentioned that if the blood you see after sex is bright and pink, it's likely superficial and from the tearing. Also, my bf is fairly large and her advice was just to make sure you're really ready 'down there' before you start having sex.
I hope that eases your mind a bit. But again, the take home message is that even though I know my bf well and we haven't participated in any risky activties, I still went to get checked to make sure I was healthy (and also for my sanity).
Please go and see a doctor to rule out sti! Do you have any other symptoms such as burning pain while urinating if so it could be a episode of herpes. Friction during sex can bring out an episode and the fact that it still hurts a week later is worrying!
This is not normal. Either your boyfriend is too big for you, or he is being too rough. You should really go get it looked at by a doctor, because if it is tearing at the entrance it could be tearing somewhere else too. The wall between your vagina and your anus is very thin, and could easily tear if you have too violent sex. If this were to happen you could get either very bad infections or even a sexually transmitted disease. I would highly advise going to a gyno. doctor.
Hope this is helpful :)