Hi.
I have just been through the same situation, apparently. My problem was that I had been depressed for almost two years and had had no sexual life therefore in a way it was as if I was a virgin again. And it was so painful to use a tampax or have anything inside for that matter. I started dating this guy about two months ago and we just couldn't do it. He would finger me but it hurt like hell. The thing went on for about a month of trying and it seems to be the only way to enable you to have intercourse. Given that the vaginal muscle is one of the most elastic ones in the human body it just needs some exercise to loosen. Your boyfriend has got to be patient though. So just keep trying, it is the only way, and relax and think that by definition things much bigger than a finger or a penis can go in the vagina.
You will enjoy it.
By the way how old are you ? Is this the first time you are getting physical with a guy?
Hope this helped,

I had a similar problem . . . i just kept trying with a tampon over and over til i could finally get one in. i think that will help you. it was a little uncomfortable at first, but then it was fine. use a mirror to help see where you need to put it, and also what helps is taking a deep breath and relaxing. sometimes you unknowingly tighten those muscles when you are nervuos or scared. just DON'T try to put in a tampon when you aren't on your period... it will hurt because the entrance isn't lubricated at all. good luck!