lube,lube,lube. this will help some. you need to relax and take it slow. no wham bam thanks mam. is he extra big? that will make it harder to enter.

I know how that is... If you're still having problems with it... try what my fiance and I did. The first time we had sex he couldn't go in because I was too tight and it hurt. (you're bf will need A LOT of patience for this.) If you're more comfortable on the bottom (like i was) Have him go in until it hurts. Have him hold his position to let you get used to his size. When you catch your breath or it's not as painful.. have him go in a little more then hold... keep doing this until he is all the way in. It may hurt a little when he starts to move but make sure he's going soft and slow at first until you want him to speed the hell up. (it may take a few min but it's worth it)

Ah, a question in my area of expertise. lol.

I've been having sex for like a a little over a year now. Not very frequent, but still having it.
Everytime we did it, it hurt like an SOB. If it actually managed to go in, in only went in like an inch. Very very frustrating on both of our behalfs. After the second time I went to the gyno thinking there was something wrong. Other than being narrow, there's nothing wrong with me. He did suggest a different lube. He suggested Astroglide, which I have to admit, helped some.
But we tried again, and still only like an inch... just a little less painful because of the different lube. I tried on top, on bottom, from behind. No luck.

I went to friends (and here) looking for advice. I had my fair share of toys already, and some would go in, but they were on the skinny side so they didn't really help much.
So I asked everyone if a different kind of toy would help. Most suggested a jelly dildo. Me, being very frustrated by now, figured why the hell not and I ordered one.
I had trouble when I got it. I in fact gave up. But then like a couple weeks or so after that me and him were talking and I said it was still hurting but I'd try it again that night. Low and behold the damn thing went in. It hurt a little at first, but still, went in, with of course the help of Astroglide. Now it goes in every time. A little difficult at first but no problem after that.
Granted, I haven't tried it with him again yet (that's hopefully coming soon), but it's at least a start.

So, enough babbling from me. I suggest something like a jelly dildo. It can't of course compare to the real thing, but it can at least help some. Try to find one that's about his size, which will help even further.
And of course the lube. I say Astroglide. Some people swear by WET and other similar products.
Use things like tampons if you don't already. They'll at least get you used to something being inserted in you.
And of course, as the person above me said, foreplay. Get yourself worked up. I'd tell you to relax, but I know that's easier said than done. If you've had painful sex in the past you're going to clinch up before hand because your mind knows it's gonna hurt and that causes a reaction.

more foreplay! it helps relax you and makes everything last long and feel better