Is it legal?

Ok, so my boyfriend is 15 (turning 16 in like 2 months) and I'm 17, turning 18 in June. My question is, will it be illegal for me to go out with him once I'm 18? One of my friends said as long as I didnt meet him or start dating him once I was 18, it was fine. But I'm not too sure, and like he has a child service worker bc of some family problems so my mom said that itll cause problems. I really dont want to leave him, we been together for a while and dont want to leave him. Hes so mature and nice and we've already got plans for the future. But I don't want issues either. So any of you got there that know of law, be it work or school, would it be illegal to date him once I'm 18?