Help!! Is He Bipolar???

Ive been dating my best friend for a little over 2 years. I love him more than anything in the world, but its getting to the point where his actions are making me hate him, and starting to make me hate myself a bit. He was diagnosed with depression when he was younger. What im wondering is if it is possible that his doctors compleatly missed the manic part, because my boyfriend himself doesnt even seem to be remotly aware of it when it happens.

Here are my reasons for thinking he might be bipolar. Any feedback would be greatly appreciated, because I want to make sure its a strong possibility before I try and confront him about it needlessly.

Since I have met him, one word I would use to describe him is moody as all hell.

60% of the time he is mildly depressed. Sleeping in, always tired, no motivation, not much of an appitite. Just generaly blah. If I have to be honest, this is my fave "mood" he gets in, because he is awre that he is depressed and is willing to let me hold him and love him and I can get smiles out of him occasionaly. He also makes it very known how much he deeply loves me and cares about me, and how he needs me or he really would be worthless.

15% of the time its bad depression. He curls up in the fetal possition, doesnt respond to the things I say. Its almost as if he isnt there. One time when he was like this, he said that he didnt want to live anymore, and he swallowed a bottle of his dads sleeping pills. I called the police, and they took him to the hospital. Too bad he blaimes me for that... I was just trying to help. I dont want to see my boyfriend die!!

5% he is compleatly normal. Loveing, kind, somewhat motivated, and one might even think he could be seen as a normal happy person.

18% of the time, its like there is a whole diff person taking over his body!!! I can see when he's starting to get into what I assume to be his "manic" moods, because his jaw starts clenching, and his normaly rather squinty eyes get somewhat larger and more alert. When he is like this, I see him staying up till 6-7 in the morning. He is very irritable. If we are out in public, sometimes he will talk so loudly about something compleatly irrelivent that me and my friends look at each other like, "whats going on? What is he talking about? Why is he getting upset?" I feel bad to say this but he embarasses me a lot. Sometimes he tells me that he thinks he is smarter than everyone else in the world, and then begins to talk down to me as almost inferior. While I hate the fact that he talks down to me in those moods, I must admit, its almost nice to see him somewhat self confident when im used to seeing a depressed and insecure man.

And when he drinks... Omg! He tells me he doesnt have an alcohol problem, because its true, he only drinks maybe once every few weeks. But when he does drink, I cant get him to stop. Even tho he may not be addicted to it, it is a problem. If there is only beer avalible, there is only so much his stomach will hold, so he cant get too drunk, but it still brings out the most annoying side of his "mania" sometimes it even comes out after only half of a beer. Which makes me wonder... Hes not drunk, where is this all coming from?? But when he drinks liquor, he is unstopable. One time his father and brother had to hold him down so someone could hose him down to maybe make him calm down. Another time, we were out at the bar, and he saw me looking over at the bartender behind the bar. I was just signaling him for another round, but my bf went off, screaming at the top of his lungs that I was a prostitute! And that I wanted to sleep with everyone in the bar. Extreamly embarassing. He also tried to pick a fight with the bouncer who thru him out that was about 3 times his size =( when we got out of the bar he started walking off by himself screaming out some very depressing nine inch nails lyrics, and crying. I convince him to get in the car with me, he is saying that I dont deserve to live, and its pointless for him to live, so he grabbs the wheel while im driving and tries to steer me into oncoming traffic. When I regained control and screemed, "are you crazy?!?!?" he got real quiet, looked very offended, and then jumped out of the moving car going 35 mph. I left him there to walk home by himself, I wasnt going to endager my life anymore. Next morning he doesnt remember, claims im lying, then starts crying and appologizing.

I feel like im walking on eggshells with him. I find myself hiding very insignificant things from him for fear of sending him off into a tailspin. This has been an emotional rollercoaster from hell. It must be increadibly hard to be bipolar!!! Just dating someone who has it is exausting! I feel my energy and happyness being sucked away. My friends and family want me to drop him. With all of his sweet words, and then his verbal abuse, and pulling close and pushing away has worn me down to where the thought of him makes me sick to my stomach sometimes. =(

so what do you think, does this sound like bipolar? If so, how do I go about telling him? He seems to be scared of me calling him crazy, so I was wondering the most tactful way of approching him.