So many messy ingredients in this scenario...first off...sex before marriage is a great way to mess up your future together. I know in the minds of the masses this is a school-marschisch (is that the word?) perspective, but as you yourself have found out, it's not the way to go. Moving in together is also a great way to ensure your marriage is likely to be mediocre at best...the reasons for this are many and I'll not go into it here and now.
Living at her parent's house sucks x 100. It's not hard to see you both are way too young to be dealing with these issues successfully. As hard as it may seem, the best thing I see would be for you to get the hell out of her parent's house and learn to stand on your own two feet...this may take a few years. This will give her the opportunity to heal from the turmoil, and mature in her own situation.
Without sex, and not living together, especially living under her families roof, you two can start dating, taking all the steps really slowly (long walks, holding hands...etc etc...these steps are not to be rushed past). From this position, the thought of marriage in the future becomes realistic and viable...something to talk about after courting with her for...say 12 months. Seems to me you both foolishly jumped to the end (living together, children etc...) and now have trouble figuring out what is the beginning. Seems to me your idea of "marriage" is something twisted and deformed...both of you clearly haven't the first clue as to what marriage is, or how to build one in a way that will with-stand the storms of life.
Your child will cost you shit-loads of money. Before you get yourself into more of the same mess yet again, I suggest you give yourself a year or two until you've woken up to just how much trouble you're already in, and the extent of the damage that's coming your way...it is coming. Don't add to it.
Best wishes always.