Alright, to start off, I am 19 years old, and I have been sexual active for about a year now. Well, technically, I have had sex sparring over a year's time.
Anyway, my boyfriend and I have been sexually active quite frequently for about a month now. It's been great, but there has been one thing that's been happening recently. After we have sex, and we are ready for another round, my boyfriend cannot go inside me fully again. As a matter of fact, he doesn't even go in an inch. It's like my vagina made a wall in less than fifteen minutes! We managed to fix the problem with a whoooole lot of lubrication. (And it's not that I wasn't wet, he could put a finger in me no problem!)
Does anyone have any idea what's going on?

Are you having an orgasm every time? The vaginal muscles will tighten up as you are building to the orgasm, and the sensation for a guy is like you're trying to push him out. I always assumed it was nature's way helping the guy along. But it's normal for the muscles to relax after you come.

There's an interesting thing that happens to a young woman when she starts being sexually active, it's like her vagina "learns" how to respond to a man during intercourse. This is probably part of your normal process.

As long as you are not in pain, there's probably no problem. But I'm not an expert. You may want to talk to your ob/gyn about it, or experiment with a vibrator to understand more about how your vaginal muscles respond to different kinds of stimulation.

Ah youth! Enjoy it while you can. When you get older those days of him being able to make it 5 or 6 times in a row will become a pleasant, distant memory. I think Richard is on the right track, a little in between (fore)play would probably not go amiss. It's not just wetness, which at that point is partially his ejaculate, it's your arrousal. Your body is still glowing from the first round and may just need a little time to relax.

Richard S: Well, there are times when I don't orgasm, but I come pretty close. And it's so frustrating when I don't. Not to mention, he gets mad at himself, thinking he's not doing his "job".

Wildchild: Unfortunately, I can't afford birth control at the moment, so we have to use a condom. (Ugh, condoms.) So I know, or hope, it's not his ejaculation.

Foreplay is quite common with us, and it last a good thirty minutes to an hour before actual intercourse. When we go for a second round, there is lite foreplay, about fifteen minutes or so. Should we lengthen the foreplay when we go for a second round?

I'm not familiar with what social services you have available, but here in the western states we have county health services where various methods of birth control and STD testing are available for little or no cost. Planned Parenthood is usually very reasonable too. Even if you continue using condoms, you should have some other form of more reliable birth control since condoms can break or slip.

Can you orgasm with foreplay or masterbation? Often that comes first. If you can get a copy of Drs Steve and Vera Bodansky's books on Extended Massive Orgasm, I think you would find some good info. They explain that research has found that many women have orgams without knowing it because they are expecting a Hollywood experience. Orgasms can be mind blowing or they can be a nice glow. Once you are confident you've had some, you'll connect to them and experience them more fully. Relax, you could be suffering from performance concerns. Practice makes perfect, just have fun, love, laugh, tickle, enjoy yourselves.