As a fellow 19-year-old who is a father, I think I can provide you with some advice here.
After this moment has passed, and you’re either an expectant father or a nerve-wracked, horny teenager, you HAVE to sit down and talk with her as to what you are both comfortable with as far as birth control is concerned. If you would like to do some comparison shopping, I would recommend Go Ask Alice!, the Q & A site for Columbia University’s Health Center. Lots of good information, and it’s kept very much up-to-date.
I would recommend you use condoms and she be on the pill as the easiest and probably most affordable system of dual birth control, though condoms can get to be expensive if you’re both really horny.
You’ve said you’re willing to use condoms, and I highly recommend it; shop around a little bit and find the one that works best for you (and this is the most fun you’ll ever have comparing things - shopping for appliances is downright boring in comparison). If she is on the pill - and this would fit into the category of “important” - she has to take them same time every day, and if she gets sick and vomits or has diarrhea, then be extra cautious.
I’m not saying pregnancy would be the end of the world for you, because most likely, it wouldn’t be. But it would be much, much easier in, say, 10 years, when you have your own job and your own house and your own life. Natalie and I were lucky, in that with parental support (read: checks and the occasional emotional comfort when they’re not berating me about one thing or another) we have made this work. I’m still in school (listen to Mr. T), she’s going into nursing in the fall, we have a nice apartment in a good part of town, and Michael will be a very happy 5-month-old in two days.
All the same, sit down and COMMUNICATE as to what you both want out of a sex life. It can be lots of happy slappy fun, if you’re into that sort of thing, but it’s most fun when you’re not looking over your shoulder every day at the thought of possibly getting her pregnant.
Oh, and should she be in the hospital with appendicitis, and she’s crying, and she wants to tell you something but she can’t, and you’re trying to coax it out of her, don’t say: “Well, it’s not like you’re pregnant, right?” Trust me on this one. Bad idea. 
(Sorry if this rambles incoherently at 3 AM, but I hope it was helpful or at least entertaining.)