My ex says he’s changed and wants marriage—should I trust him again?

I left him over a year ago because he became terrible. He claims he treated me terrible because he was convinced I cheated. He says he's been in therapy and is a better person. He has had a relationship since we broke up so I don't see how's he's been doing the work to actually change. He said he realized he can't replace me and he wants to get married and start a family. I use to want to marry him. But I can't see myself trusting him again. He asked me to let him prove himself to me. But I fear he'll fake it just to get me then become terrible again. I don't know if it's worth putting time and effort. He really had me in a dark place last year but things with him use to be amazing.

My ex says he’s changed and wants marriage—should I trust him again?
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