gay friend problems

MeiLi
I am best friends with a guy named Marcus. I met him when I transfered schools back in October. Everything was going good in our friendship, until now. I am just starting to realize how much he is trying to control my life. He also does things that I feel like friends shouldn't do to one another. Last weekend I was hanging out with my friend and he literally just showed up there uninvited and was just like I'm hanging out with you. Well, we went and hung out with my friends friends   Well, marcus then proceeds to tell everyone about how many guys I've slept with and that was not okay with me. I can now only imaging how many people he has told. Another thing that he does that bugs me is hanging out with MY friends without me. I don't know about any of you other ladies, but to me that's just not right. I don't really know what to do anymore, like I know I need to talk to him, but that's really hard for me to do. I am very shy and it's really hard for me to confront people. Any ideas how I could do this gentlly? I feel like me trying to talk to him about this is going to ruin our friendship, but at the same time its putting me in a really bad depression too.