Sex is extremely painful and isn't getting better - why?

I had a bad experience on a night out about six months ago where I didn't want to have sex, but I was too drunk to be able to stop it. I am in a loving relationship and was at the time, and we are still together, and I've have had to tell him the truth recently because it's getting harder to hide, since whenever we have sex it's very, very painful. It almost feels like losing my virginity all over again every time we do it. I need to stress that he is a very gentle, loving, sweet partner; he isn't rough or insensitive in the slightest. But it doesn't make any difference. I put off having sex with him for a few months afterward the incident because I was wary about whether it would hurt or not. It wasn't too hard since I'm a student in another city and we only see each other about twice a month. In the last three months of resuming a sexual relationship I have hoped that whatever it was would go away, or heal, but nothing is changing and I can't keep on like this.

The pain is instant, from the moment of penetration. It doesn't hurt always during but there are a few moments I have to ask my partner to slow down or stop. Afterwards it is very painful and it doesn't go away for about half an hour. Nothing is torn. It doesn't feel like a cut, it just feels like he doesn't fit. Always, every single time.

I know most of you will advise I should see a doctor. I'm just scared, I don't want to hear something horrible and I just hate the thought of the whole thing. I know I can't leave things as they are...but can someone maybe shed some light on this please?