Am I the other girl?

I am 16, he is 21. I've known this guy for years and he's been nothing but a good dear friend to me. He's helped me through a lot of shit. When my dad was hospitalized, he stayed up on the phone with me all night making me laugh instead of cry. When I was abused from my exboyfriend, he was there to help me out and threatened the guy to stay away from me.

Last year we decided that he's going to wait for me to turn 18 and then we will be officially boyfriend and girlfriend in a full relationship. We both understand that two years is a long time and a lot can happen (especially me because I always bring it up and remind him it's okay if he wants to date other girls or have sex with someone who isn't me). He always says I'm the girl for him but apart of me knows the reality of this situation.

Well, recently my friends were on Facebook and on the people you may know list they saw his name. When they clicked his profile the profile picture was him with another girl in his arms kissing him. His relationship status said "engaged to" and their anniversary was last May- right before he began discussing being officially my boyfriend. At first I thought nothing of it. It isn't like he and I were official. I understood the situation. But because he still treated me like a princess (which I ain't complaining about...) I was really curious about the whole negagement.

So I asked one of our mutual friends to investigate for me. They asked him and he said it was nothing...

After a month I noticed his profile was gone but the girl's was still up. And she kept posting more and more statuses about them and pictures too. I finalyl had enough so I called him up and told him I knew. I said I was pissed off because I kept reminding him I wouldn't get mad if he just was straight up with me about it all.

He got super defensive with me. Never actually answered any questions. I said whatever and we dropped the conversation.

A month later and I was on my facebook and who comes up on the sidebar? The girl he's supposedly engaged to! I had enough and again called him up flipping out. He told me he'd take care of it and he never denied nor said he was engaged... Which makes everything even more fishy.

I can't lose him and honestly I do love this guy. It might sound stupid but it's true I do love him and how he treats me. But I can't stand all this lying and avoiding. Everyone hates him because he sort of does act like an ass when ti comes to being in my life. Because of his career in music he travels a lot. So at times nobody will hear from him while he's overseas.

If you think about it, he and I are like Carrie Bradshaw and Mr. Big from Sex and the City. Literally, that is us to a T.

I just need some advice on what to do next. How can I shake it off? Should I inbox or add the girl on facebook and explain to her the situation?

Help? Thanks.