<human>: to premise.. ive been in a few relationships where ive been emotionally and physically cheated on.

we've been together for 5 months. we spend pretty much every day together but there have been quite a few night recently where she didnt even call me before bed, which is completely not her, she even complains if i make her wait to say goodnight to me on the phone..

a few times while sitting with her, ive seen a guy send her some questionable messages. i asked if he had any feelings for her, but she said hes never been anything but a friend, and that her last boyfriend got suspicious over this and it fucked things up. 

so i moved past it.. 

then i was over at her place tonight. her cat jumped up on her laptop which turned on the screen, and of course her messages with him were open.. i saw the couple lines on the screen.. saying how all he wanted for christmas was her and that he still loves her.

i got pretty pissed so i got in my car. my girlfriend and i argued in the driveway for over an hour.. she claims she only keeps him around because he threatens to kill himself if he loses her as a friend. but if that was the case then why did she tell me the times before that hes only ever been a friend? 

eventually her mom comes out, tells me she thought i was better than the other guys she dated and that she would never cheat on me.. but why am i struggling so much to believe?

i just feel like total trash now.. because either im getting cheated on.. or i just accused the girl I love that I'm cheating on her.

I don't really have much of a family, she's pretty much all ive got for emotional support. this is the first time ive had someone to celebrate christmas with since I was 16, and now I just want to crawl into a hole and cry

Can you summarize the given text in a few sentences?
<bot>: this guy is either hooking up with my girlfriend, or threatening to kill himself to keep her in his life. and i blew up about the whole thing