<human>: Can you give me the gist of the text in a nutshell?

So, my boyfriend and I are generally pretty open with our phones and things like that, he goes through mine all the time. I finally decided to go through his, and I genuinely didn't expect to find anything bad. But one look at his Facebook messenger and I was feeling pretty different. I found out that throughout our whole relationship he'd been messaging tons of girls, sometimes just saying "Heyyy," sometimes saying things like "you're so cute" "I love you" and "wanna skype?" 

Here's the thing: i realize how petty this problem sounds, because I'm certain that he's not actually cheating and I know he doesn't reallywant to. But it upset me that he seemed to be so devoted to me and said he didn't talk to other girls like that, but he'd turn around and do it just for attention. Especially when I couldn't even bring myself to talk to another guy like that if I tried. 

When I confronted him about it he cried and cried and said "Please don't leave me" "I'm so sorry I'll never do it again" "I'm such a fuck up" until I was the one consoling him. After a few days we somewhat moved on but now I see him as a completely different person. I had no idea he was that immature. On top of that it's hard for me to trust him. And honestly I've become an extremely jealous person. 

I know that we can work through it because I truly do love him and I don't think he'll do this again. It's been a few weeks and I feel a lot better now. But I still have trouble believing things he says and I don't see him as the respectable person I once did. Please try not to suggest dumping him, because I definitely don't want to do that. I'm just looking for advice on how to trust again and move on from this.
<bot>: Boyfriend was flirting with other girls through messenger, now I view him differently and i don't really trust what he says. How can we work on these problems?