Whoah there fellahs easy there chill out.
Ok if you are really really worried about her age check what the age of consent laws are in your state. Some states are 18 but others are 17 and 16. It's about half 18 and half 16. A couple states are 14. This isn't an official legal service but it might help you relax.
http://www.ageofconsent.com/ageofconsent.htm
Second of all, don't make such a big deal about it. No doubt the relationship was 100% concentual. You're only 22 yourself and she lied to you. Are they going to prosecute her for lying? If they do then they really are stark raving mad. If they prosecute you they are equally mad. Who would look after her and the baby? It would be pointless and stupid and would ruin everyone's lives involved. Loads of women go through college and have a child. Wait on it and she'll be 18 in no time and then reveal your relationship if you can. Have you met any of her family? If so or if not try to develop a good rapport with them. When I was 24 I dated a girl who was 17 a month or two before she turned 18. We abstained through the whole relationship though but god I loved her HARD and her Dad thought I was great. Society tried to make me feel my love was ingenuine, but it wasn't. Since then I have dated older women (of course) that are far less mature, learned and suiting to me.
However, lying to you, is immature, is a bad foot to get off on and not exactly a woman you want to rush into marriage with, but you may have a child coming, if you aren't going to take that one unpleasant way out. No doubt if she does decide to have the baby you'll probably have graduated and with a job by then. Settle down. It's life. People used to get married in their teens all the time and some still do in the US and in many countries. There are even Americans or former Americans/British who live on an Island in the Carribean where they marry at as young as 14! It's normal no matter what society and their draconian laws try to make us think. Remember it's society that is changing not human nature. Just looked how messed up they made the world eh?