What do I do after sex? Should I just lay there? Should I talk about it?

I am a 19-year-old college student and am seriously involved with my boyfriend who is a 20-year-old college student. We have even talked of getting married someday. Our relationship is very close and we talk about everything, and he is very wonderful and supportive. I feel very committed to him and would really like to have sex with him. We have tried twice, but it hasn't really worked out because my vagina is too tight. I am pretty sure the problem is just that it needs to be stretched more, because I have been to the gynecologist and don't have any infections. He says that he is okay with whatever we do and that he loves me no matter what, but I still feel guilty about not being able to go all the way. How do I get over this guilt? I will be leaving college for the summer soon and we will be separated for awhile and I want to make sure that our relationship is as solid as possible before I leave so we have the absolute best chances of surviving the summer!

I am an 18-year-old male. And I lost my ability to reproduce in a bull riding accident at a rodeo I competed in about two years ago. I would like to father children more than anything. And now I have a girlfriend who is talking of wanting to have kids in the future. But I can't bring myself to tell her that I can't because I still haven't dealt with the problem of coping with it myself. I need to know how to deal with the fact I cannot have kids, especially now that my significant other wants them, but is ignorant to the fact that I am sterile. Please help me ASAP! This is tearing me apart.