1st of all I think you and your gf should have a talk, maybe you and her should go see the doctor and seek advice,
ask her if she wants the baby or not,
having a baby at 18 will b realy hard, im in the same possition all tho ive decided I want to keep this baby, I know it will b realy hard but at the end of the day if your big enough to have unprotected sex then you big enough to face up to things,
i hope everything goes well 4 u n ur gf xxx