As I mention to all women in this position - Google 'cycle of domestic violence' (it's a lot to write).
As Hawkeye suggested, get a circle of support. Fear of doing it alone is keeping you in an unhealthy relationship. Taking one small step at a time can lead you to see that you can do it without him.
I wonder where your family is in all this?
As for whether he'll stick around - 10 years ago, studies showed that 90% of men who marry in their teens divorced within 10 years. I've little doubt (seeing as the world has become more complicated) that statistic is now even higher. Ie. Don't count on him to stick around, whatever you do.
The trick you'll find is, you've put yourself in a position where you'll have to grow up, fast...while he'll only be in that position by his choice (and whatever child support he may have to pay).
Do what is best for you, and your child (which by the way, may, or may not be, adoption). Good luck.