I've been sleeping with someone for about two years, and we recently started to get serious. He's been having trouble trusting me because I hang out with guys. I do not get along too well with girls, so most of my friends are guys. He thinks that my guy friends are only my friend because they want/hope to have sex with me. Am I being naïve or is he right? And should I continue on trying to pursue a relationship with someone who doesn't trust me?

Make a choice if you want him and tell him you mean it.

He knows that I want to be in a relationship with him. I just don't understand that he wants me to stop hanging out with my guy friends but he doesn't want to call me his girlfriend.

Then just stop hanging out with your guy friends. I don't see why this is an issue with you. You are a woman who hangs out with men. If I was a guy that would send up red flags. Like, why is she hanging out with men? You don't see his point? I do. Why should he commit to you under the circumstances?
Wow, so many questions !

He doesn't want to call you his girlfriend after sleeping with you for two years??
Hmm. Is this a chicken/egg thing - he won't call it serious until you drop the male friends, or what? You need to ask him, talk about this, we can't solve this until you know where he stands. And you are the only one who can decide if you will trade the friends for status of girlfriend. I suppose you could get affadavits from each of the guys saying they aren't trying to sleep with you (kidding, sort of.. )

So he is cheating, and you help him. No wonder he doesn't trust guys. Cheaters seldom can trust anyone. He must be serious about keeping you on the side, and in the sack.

He doesn't have trust issues he has cheating issues. Not sure what your issues are, naïve?? That's a start!