What am I supposed to do? I'm in desperation.?

I guess this is happening to me because he's my first love but I'm having huge problems with him. This guy and I met last summer. He used to be crazy for me. However the miles separating got in the way...not to mention all the girls too. Yeah everyone told me he's a player but I ignored them and fell head first for him. I'm completely emotionally invested in him. I've tried to tell him goodbye only to come crawling back because I don't know how to live without him. Aside from the fact that he's a major ladies man, I love everything about him. We've been flirting for almost a whole year and getting closer. But, throughout that time he's been in and out of relationships. Also, he want's me to do stuff with him this summer and we were trying to come up with a way to be a able to and he told me I'd be his girlfriend if I did. I'm convinced I love him so I want to but the problem is that he doesn't care about me as much as he used to. What do I do? I was going to try being friends with his sister in hopes that she would knowingly help me but I just don't know what to do please help.