<human>: So my girlfriend just called me really upset and said that her ex was outside her house, like he kinda just showed up unannounced like right before he was going to work. Even though she has told him MULTIPLE times that she has a boyfriend, he just shows up unannounced and does this. He then apparently tried to kiss her, she stopped him and told him again that she has a boyfriend and won't do that to me, and she told me directly and sounded really mad on the phone with me, I don't know what to think about this I had to get off the phone, but I called her back up and ask her if she would just stop talking to that guy, and she said she would but, he kind of just did this out of the blue. But she still said she quit talking to him, because he was there for herwhen she was going through some bad shit, before I met her and she just wanted to hang on and not push him completely away, but he won't take the hint that she has a boyfriend.

I'm like really worried that she's cheating on me, even though she swears up and down that she never would, and every time somebody has contacted her, be that an Ex or just some guy offline, she's always told me straight up about them, 
what happened, and that she told them she has a boyfriend. but she started crying because she is just frustrated because I can't just trust her, and I'm sorry that I don't know how to just trust but when you've been screwed as many times in life as I have, it's easy to get a complex about it.

So is she cheating on me? She said one of the first times I talked to her that she hated cheaters, and she's been cheated on before and I don't know if somebody that has been cheated on before, we just do it to another person? I don't know what to feel, someone please help.

Could you distill the essence of the text into 1-3 sentences?
<bot>: my girlfriends ex tried to kiss her tonight, she straight up told me about it and every other time a guy has tried to weasel in with her, but this guy won't leave her alone, so is she possibly cheating?