Will a 18 year old be arrested for being put on the birth certificate of a child he conceived with a 15 year old?

You're not a slut. And it depends on what state you're in. In most places, someone needs to press charges first. My boyfriend is 17 and I am 15, he signed the birth certificate and is not in jail. Although your boyfriend is 18, 16 is still the legal sex age in most places. I am under that and he is above and nothing happened to him.