You will be ok. I don't know anything about your marriage, but just because you married for the wrong reasons doesn't mean it is doomed. It means that like every marriage, you need to work at it. It is worth it or it isn't but your husband isn't a JW, is he? Plus. You are not baptised. PLUS. You haven't done anything other than the marriage that changes your status-you didn't go awol from army, right? You are twenty. You will do fine.
As to eternity. Read scripture, Value Wisdom when you recognize it, pay attention to where you are getting your information, don't accept things at face value. Pray. Even if you don't know about God, pray, pour out your concerns and your issues and your joys and your sorrows. Use it as a kind of therapy (I've always thought that prayer is more about us pouring it out than God needing to hear-he already knows it all).
Talk to your husband and see how he feels about the marriage. It's HIS life too. If there is love between the two of you, an early marriage is not fatal. And neither is an early divorce if that is what you decide on. Use birth control until you have figured that bit out. Nothing is guaranteed, but at this point, I think it wise to hold off on that particular joy.
Take care!