>>715684391 (OP)When the baby is born get a DNA test.
1. Being young and having kids is fine and better than being old and having kids where you don't even get time to grow up with them
2. You will both be closer in age so you grow up with similar cultural interests
3. Having kids is a natural part of life
4. You don't have to marry that girl, but you will have to be the father to the child (if it is indeed your baby, seeing as how she fucks unprotected it might not be yours)