I really appreciate everyone's advice and concern for my problem. I think I've made up my mind, and I won't push or even talk about it anymore. It seems likely that our 4 year relationship will just get worse if I do. I don't want that, and it's just not worth losing her over something like this.
Again, thanks everyone.
Confusion123
Don't push her. Just be understanding and patient.
I was in the same situation before ( I was in the same place as your girl friend). I was dating a really good friend at the time who I really cared about. I wasn't ready he was and we broke up. Now we are not friends anymore or anything else.We had a lot of potential. I was almost ready but he made such a big deal about it and pushed so hard- even involving others. It ruined everything.
So, if you really care about this person, give her time. Once you do it, you will have time to do it over and over again and you won't even remember the long wait.
lucasjr nailed it as did penswriter.
Jim
I completely agree with penswriter. Perhaps you can explore other options - mutual masturbation can be a really good substitute for intercourse. Patience is best at this point - I know it can be torture at times, but it'll be worth it. If she gave in to you just for your sake, there's a strong chance she'll regret it and, in turn, harbor some resentment towards you. You two have been together a long time - maybe she's hoping to make it a more permanent relationship before she moves forward sexually. Or, maybe, she's just being pragmatic and knows there is no sure way to prevent pregnancy except abstinence - and she's terrified of having a child at this age.
Don't try to convince her. Let her be ready in her own time. Push her...and she'll run or regret it for the rest of her life.