<human>: Two days ago I broke up with my boyfriend of 4 months and I'm constantly doubting my decision. I decided to end it because I hate the way he acts when we argue; it's as if he turns into a bitter, angry version of himself that can't be reached. That leaves me feeling alone, and on multiple occasions made me feel like breaking up was inevitable (only to have the feeling go away when we got along). And a few times when I've brought up issues, he's discounted them (i.e. "it wasn't as big a deal as you think, nobody noticed"), making me feel like he doesn't truly respect my opinions. 

I've brought it up to him before that I hate how he acts when he's angry, only to get rebuffed. He gets very defensive. Though, I was never able to effectively communicate what it is he does, just that "I don't like the way you act when you're angry" and "it's like you're another person". I feel like I should have tried harder. When I broke up with him he said he didn't realize I was that upset about it (even though I've voiced how upset it made me nearly every time he got angry) and that he thought it was a stupid decision to make without trying to work on it.

Can you condense the text into a few key points?
<bot>: Broke up with boyfriend over anger issues, unsure if they are an unchangeable part of him and having doubts.