It's OK bro, I know the feels. Stop worrying about the past as well, it has absolutely no added value. I know it's not just a button you can turn off. There's two options here, you either really face those things that you feel shit about in the past and this time go through them properly (such as talking to people you feel you've upset or something), or gradually try to not give a fuck about them anymore since they're just holding you back for nothing. The past is the past, set yourself goals for the future. Compensate the things you feel shit about with good things. Make a list of the things you feel shit about and find something for every one of them you want to achieve to compensate it. Achieving your goals will gradually balance you out.
I'll give you an example of myself. I always was a smart guy but I got so bored at school that I didn't do shit. I managed to get though it but I always thought deep in my mind that it was pure luck and I actually wasn't intelligent at all. (Looking back there's no way I could've gone through it without intelligence but hey). I set myself a goal to get a Master Degree like a fuckin maestro. I recently got my MSc degree with distinction. It was a struggle mentally with insecurities and flight behavior, but it felt fuckin good once I finished. It took away all those insecurities.