Okay so I started talking to this guy for a few weeks and then we dated for two months then I broke up with him because he smacked my butt and my sister told me to, then we me and him kept talking and stuff getting really close then he dated this girl who kept cheating on him and they broke up like a billion times and kept getting back together and everyone hated her. Then he kept saying he wanted to end his life and I was the one he told his secrets to and the only one he trusted and even when we were friends we said I love you and gave each other little kisses and we were never seperated unless I didnt have him in a class. And then we dated again and he broke up with me a few weeks later dating the same girl he dated many times when everyone told him not to. Then they kept breaking up and getting back together and he kept saying he wanted to die and that I was the only one keeping him alive and all that. Now we are closer than ever texting all the time knowing everything about each other and every time I try to date someone I always go back to him and he does the same with me and now I feel like I don't belong with anyone else and that he's the one but I'm afraid to be in a relationship now in fear of that person wanting to kill themself and making me stay with them. But I don't know if I love this person and that I belong with someone else. Oh and btw when he was with the other girl we kissed a couple times but never dated.
what do I do!?!?!?!
what do I do!?!?!?!

It's a young guys poor attempt at manipulation. I knew a young man who could cry on cue and used it to get away with alot of bad things he did to women. Because men don't usually burst into tears women always fell for it in a second.
And this guy wouldn't date another inbetween you if he were seriously suicidal, infact he'd already be dead.
He is a snake from the sound of it.
I have some experience with cutting off manipulative and abusive people who were threatening suicide, and this is what's worked for me.
1) Tell him it's over. I suggest that you don't do this in person. Do it over the phone or online. I know that sounds harsh, but it's a lot easier to maintain a bit of distance if the other person isn't physically there, and it's safer. If possible, you might want to have a friend sit in the room with you while you break up with him. I had a friend sit with me while I broke up with my manipulative ex over the phone. She didn't say anything, and he didn't know she was there, but just having another person in the room helped me keep things in perspective.
2) If/when he threatens suicide, call emergency medical services. Do NOT comfort him or try to dissuade him. He's threatening suicide to manipulate you. If you call 911 (or whatever the equivalent is where you live) and tell them his address (or phone number, if you don't have his address) and that he said he's going to kill himself, they'll check on him. That way, if he does try anything or is going to, he gets the help he needs. If he doesn't attempt suicide, he gets the message that if he tells you he's going to, you're not going to play games. Either way, he gets what he needs without pulling you back into it.
3) Don't let him persuade you to come back. In my experience, there are two things that have helped me a lot with this step. The first is cutting off contact after the break up, at least for a while. Block him online. Don't answer him if he calls, and block his number if possible. You can't afford to interact with him while you're emotionally vulnerable, which you probably will be after breaking up. The second thing is talking to other people about it. If there's a friend who you can talk to about what he's doing and how he reacts, that can really help keep you from losing perspective and getting sucked back in.
If you don't have anyone you feel like you can talk to about this, if you need support, or if you have any questions, shoot me an email at thestarsarejustlikelittlefish@gmail.com