Help!

So my boyfriend and I have been together for about 3 months. The first 2 months we were together and having sex went relatively smoothly and it wouldn't hurt too bad. This past month, I've been getting really sore and sometimes it hurts pretty bad during and/or after sex. It could be because whenever we are together, which is usually just on weekends because I live 2 hours away, we have a ton of sex, like at least 3-5 times a day, and he has kind of a larger penis. He thinks I should go to a doctor, but I'm just not sure about it yet. Has anyone had a similar problem?? Any advice or thoughts would be so appreciated!!