How do I go about saying this without seeming like a frigid you know what?

You know what, meaning b****. Lol. Anyway, I have been talking to this guy for a few days and I have just recently figured him out. I noticed today on facebook that the only mutual friends we have are girls, all my age and same school, and all of my closest friends. He says perverted stuff to me and I have figured out that all he wants is a slightly younger girl that will let him in her pants. I want to let him know I am not that girl and that if he ever decides he wants a REAL relationship, then maybe we can talk then, but that I am not the "easy" girl he may think I am. I'm the type of girl that wants a romantic relationship, not some sleazy one time flings. Next time he says something perverted to me I want to explain this to him, but I don't want to say it in a manor that will make him want to stop talking to me,because I really like him, I just want him to understand I'm not looking to get pregnant or in trouble, and I'm not easy. I am pretty peeved at the fact that that's all he is trying to get from me, so I want to explain this, but be as nice as I can about it. What would you say to him if you were in this situation? Thanks in advance, and sorry this was so long.