Cheating boyfriend...?, Help! Options

[Paradox of Life]

I know you people dont' like to read a lot, so I'm going to try and make this short and sweet.
*Alias name.

My boyfriend's name is *Gary. His ex-girlfriend's name is *Marion and another ex-girlfriend *Jamie. My friend, *Zachary, is going out with Jamie.

So yesterday, Zachary sent me a message saying that Gary told her he still loved her, and that he didn't want him to interfere. And he also wanted to tell me that Gary was cheating on me. And he also was going out with a girl named *Wanda. I said, "How do you know?" and he said he called Gary and asked.

I called Gary up immediately and asked him if he was going out with Wanda. He said he didn't even know who she was, and who told me that. I said Zachary did, and Gary said he wasn't even friends with him, and he was probably just trying to screw with me. He also read through his received calls, and none of them were from Zachary. So I sent Zachary a message asking for the date he called and what number he called. He didn't respond.

So I sent a message to Jamie, and she responded with this message:

"okay cause he came to my house one day ( im not trying to make you jealous) well we kind of [had sex] not technically well after he left the next day he broke up with me and then like three days later he called me and he wanted to go backout with me and because i still liked him i said yes and then he came over that day and i know he only came over cause he wantedsome so im trying to help you i don'tknow you but if you are like that if you would [have sex with] him then don't cause if you don't he is going to break up with you and as soon as you do he is going to break up with you the next day and it sux if you really like him and if you do really dolike him then i feel sorry for you cause all my friends hate him and he went out with or likes all of my friends he likes my friedn *Lauren and he went out with *Cheri he went out with *Christina and he went out with me he went out with the whole 8th grade at my school in like 1 semester and i don't talk crap about you i would like to be your friend cause your just another friend of mine he went out with and that makes like 200 of yall of my freinds that he went you that he went out with well if you want to be my friend then just tell me but you seem pretty cool well if you don't want your heart broken you better breakup with him cause after the 4th time i went out with him i just gave up i don't like him anymore!!!!!HE IS A BI TENNAGE BOY THAT IS DESPERATE FOR SEX AND THAT IS ALL HE WANTS FROM A GIRL ONCE HE GETS IT HE DUMPS HER!!!!! AND I HOPE YOU BELIEVE THAT CAUSE IM NOT LYING!!! "

I don't know what to believe. I think I'm going to give it time and see what happens. If there's anything I want to do, it's make him stop doing this to girls. I dont' want to be another girl that he just dumps like trash. I want to have something of an impact. Help! What can I do? Who should I believe?