Legality? Is that even a word, haha!?

So peoples, I have another question to pose to you guys. Ive decided the best way to get over my ex, is to start seeing another guy to get over him. Thing is, the guy Ive been talking to is 18, and Im not sure about the minor laws and such. Not really looking for an opinion (though youre welcome to state it) so much as Im looking for the actual law. Basically, wheres the line between legal and illegal? (in case its state specific, Im 15, hes 18 and we both live in Maryland)