Can't find a way to break up

I’ve been with this guy for the past 5 months, and in the beginning he was the sweetest guy I’d ever met. At first, I was skeptical as I am with everyone that enters my life, but with time I started getting to know him better and liking him more and more. As time went, we ended up having some disagreements mostly because of me being insecure from past trauma, which I’m in therapy for and I can see myself slowly healing and getting better from that. The thing is, ever since that, I haven’t had the same guy he was before. He’s become moody, sometimes rude to me, says he doesn’t have patience anymore and even though I’ve been the nicest girl he still can’t get over our past disagreements. We can be having a nice day and something will tick him off. I’ve also realized he’s like this with things in life, if something takes too long, if something goes wrong etc. This has made me feel horrible in the past days, like an agony inside that keeps wish he was like he was before and also a feeling of “hopelessness” and low self-esteem because I feel this guy didn’t truly like me, he was just infatuated by me. I know I’m not perfect, but I’m loyal, caring, supportive, friendly… I may have my moments but I truly don’t think I’m a bad person. Thing is, I’m not happy in this relationship anymore, he doesn’t seem to want to make an effort and to be honest he doesn’t seem to care. He says he loves and doesn’t want to break up but after a disagreement I kind of get the silent treatment and feel like I’m being punished. He had an ex that he was with for 4 years and she broke up with him and he said he was devastated, so I can tell he doesn’t even like me half as much. I want to break up but I’ve never done this in my life, I’ve always been there until the person ended things… I feel very weak that I’m not able to end things because I keep fantasizing of how it could. But I’m stuck in wanting to live this when in reality this guy can’t or won’t be flexible or let things go in order for us to grow and evolve.