I need kind, genuine advice regarding being cheated on for the first time

My boyfriend and I (22) have been together for 3.5 years but best friends since age 14. I have a strong relationship with his family and him mine. I recently found out he cheated on me. I broke up with him immediately and we have been apart for a month now. It wasn’t physical. He started regularly flirting online with this girl he met at school for maybe 2 weeks in April but then randomly started telling her he wasnt into her etc etc like completely flipped his behaviour kinda insulting her. He said he regretted what he did and was trying to “undo” things. But he never blocked her. They didn’t flirt in May but mid-late May they had some random conversations about artists and sports. Then early June he goes to their graduation party and offers to drive her home and doesn’t tell me. She found out about me and immediately contacted me and told me about it all and showed me the texts.

I don’t want anything to do with him right now. We are no contact now (i told him not to reach out for at least a year) and he has respected my wishes and done everything Ive asked. His family reached out to me devastated as well and apologized saying they have no idea why he did this because for years he has only filled their ears with me and sworn to them that he will marry me.

He started therapy, been extremely apologetic and before I requested no contact checked in on me regarding some health issues and other things.

This is a man that did everything for me our entire lives knowing each other. Came to my house to take care of me when I was sick, financially supported me without question despite us being young, living with our parents and unmarried, took my younger siblings on “dates”, ran after the train when I got on, did everything he could every day to support me. I know I’m reminiscing but I was completely blindsided by this.

A big part of me genuinely believes he will never do this again and that he is sincere in fixing his issues to become the man I deserved. And I know his family has reprimanded him daily (his brothers beat him up).

Basically I’m asking if I’m being stubborn and stupid to think maybe one day we will reconnect and do it right, or if this is a more unique case.

Please be kind, this is still fresh and I’m trying to approach it level-headedly