As I can see you ahve a really nice and caring boyfrined , and I guess it helps a lot when having sex. NOw let me give you several advices, since I have similar problem (being too tight) every time I do not have sex regularry.
First of all, the more you relax the more chance you will enjoy. If you exhale when he penetrates you, it can help also you vaginal muscles to relax. As you know yourself, it is really good to have long forplay, to have you very very excited, and only then penetrate. What I personally like is to cum before a guy penetrates me. After orgasm, my muscles are even more relaxed, so he can slide in easier.
If your clit is sensitive, as it is case in most woman, try to stimulate it when he penetrates you.
Now for all penetration do slow down, to the extend that you slow down almost to no motion. What helps me is that when a guy penetrate me, he just does not move for a while. It gives me time to get used to his size. I prefer then moving my hips, all untill I am comfortable that he moves too. It is important for me to have it really slow, really slow, and when my muscles are relaxed enough and I am very excited, I can take any size.
One more technique which helps me: when I am very much arouse, my bf slides in one finger, then presses it down (I am on my back) towacts anus. That helps vaginal muscles to relax. Then he fingers me SLOWLY (being slow and getly is important) and by time adds one more finger, continues fingering and than 3 fingers. When this happened to me for the firts time, I could not believe I could take in 3 fingers....but actually I was able to take 4! If you combine it with oral, it could be an amaisng experience. So it is just about being relaxed and taking it slowly. You are more likely to be able to strech even more from what you expect.
When your boyfreind penetrates, he should first not go deep, and should definitely be very very slow, maybe sometimes stop for a moment.
Now what is extremly important with the problem you and I have, is that you are feeling comfortable enough to communicate with your boyfreind and that he is willing to be a partner in helping you feel good - which seems to be working really well between you and your boyfreind. And that is great.
And well, if all what I have written to you has not prooved to be hepful, you also might consider getting dildoes of different wight, and try to slowly strech your muscles to the wight of your boyfriend.
And if even this does not help, then, I guess you might consider a condition called vaginism, which is expereinced by some woman, and which can be help succesfully by a professional. (
www.vaginism.com) but try the above things out first, It is more likely, that you just need to strech out a bit because it is your first time.
I hope that we were able to help you in this forum, and I really hope that you will be able to enjoy your first time and have great sexual lifehttp://images.askdanandjennifer.com/forums/images/smilies/smile.gif
Good luck!