(NSFW) My boyfriend can't fit...?

Okay, about a year ago, I posted a question about my friend, Brian. He was very sarcastic and sort of had a difficult time opening up and letting down his emotional walls that he had put up. I really liked him but kept quiet because I didn’t know how he felt because he’s so difficult to read. Well, we hung out for about 8 months before he asked me on a date, and we started dating in late November. Everything has been really great. He is very sweet and attentive and he treats me so well. Well, recently, we have gotten to a more… physical point in our relationship… He is very sweet and let me take my time with this aspect because I am very shy about sex. We sort of messed around a few times and on the first time I immediately noticed how ahem big… He is… Down there. Up until about three weeks ago, though, we hadn’t had sex, we had just messed around, so it wasn’t a problem, but about three weeks ago,we decided to try. I only have had sex with one other person and I am extremely small down there. We spent probably twenty minutes just trying to ease him in down there. Lol! After about a half an hour, it felt somewhat enjoyable, but it felt extremely tight. We’ve tried seven other times since then, and every time, it takes like at least ten minutes just trying to get him in down there, and another like ten minutes of him just barely moving, just so I can get used to the feeling. I don’t know what to do. I am extremely attracted to him and I want sex with him to be fun and enjoyable, not uncomfortable, but he is massive down there. Is there anything we can do about it or basically is that just how it is? Is it possible that my body will get used to it? I’m just worried…