Please read this, I need help. I'm lost

Okay well, I guess I'll start from the beginning. I had dated my current girlfriends Bestfriend about 2 years ago. She dumped me and I found my current girlfriend, about 3 months later my girlfriend had dumped me and moved on back to her Bestfriend, then another 3 months later I got dumped again. My current girlfriend and I had found each other again later on. I then asked her out and she became my girlfriend again, she then 2 months later dumped me and the next day went out with one of my best mates. After that ended she decided to come back as I still loved her from the first time I dated her. Since then she says to everyone that she doesn't know what we are and that we are not in a relationship, while she tells some people we are, I believe we are because she said we were. Ha. We had lost our virginity to each other the second time we dated. She says she loves me but she has cheated on me many times in the past 2 months. We have been together for 6 months for the 3rd time. She constantly lies to me, I had only just found out that she has had sex with another guy while in a relationship with me, I know she has given head, hand and kissed other guys before while in a relationship before now. She blames me and tries to guilt me, over these past times I've found out these things I have tried commiting suicide. I cannot leave her as I can tell she cares but I do not know why she does these things. She is the only person I can talk to and the only person that seems to care about me. I have no friends, no family that cares so I'm pretty much alone. I worry constantly about what I'll find out next. I don't know what to do because I can't leave her. I love her too much even though I get treated like this. I have never cheated on her nor thought about it, I give her everything I can, buy her things, take her out, but I don't know. Please help.

Why is her life better than your own? Do you know how to love and care for you, not a girlfriend, you? What does what you want out of this ordeal look like? What do you want to see happen here, if you could write the script, then be the director of how this ideal situation will be played out, explain what your ideal wish would be, if even for 1 day. Go