Make sure you have regular prenatal check ups. Eat right. Drink plenty of fluids and do not over do yourself.
I was 18 when I got pregnant. In fact I was pregnant at my high school graduation and didn't even know it! The parents are tough. That is just a hurdle you'll have to overcome sooneror later. I will say that this tiny amazing child you carry will change your life, for the better. Look into home births. All three of mine were born at home and it was amazinfly empowering!