This is a pretty hard decision. And everyone's right... Only you can choose on what you want to do.
But your post was a little unclear... What are you looking for in advice? If you want to keep your baby (which it sound like you do) then get ready for a long hard journey.
But keep your head up. A lot of girls go through it alone. (man in jail, or left..One or the other) as long as you've got the support of your fam, then you'll be fine.
I was pregnant at 16 too. I did it on purpose actually (not the best thing, as I look back now) and it's going to be hard. Your life will never be the same. Just remember that you are not going to be the same person at 18 when your man gets out, and neither is he....