How do I get over my past?
The past is a tricky one. It will always be there but it can never be changed. Dwelling on things could have/ should have been causes only heartache and disappointment in our present. Instead, I offer you to look at such events and learn from them - what would you do differently next time? How can you better yourself knowing what you know now? The decisions made in the past felt like the right thing to do in that moment so please don't torture yourself about things you cannot change.
You mention regret in regards to where you could be and where you should be. It's difficult to look at the things we could have in life but I think it's important to look at exactly where you are now. How did you get there? What have you achieved? If you would like to be somewhere else then what do you need to do to get there? Can you put achievable goals into place to get to where you want to be?
'I need to be the man my wife and kids need' what does that look like to you? What are you doing at the moment that is making you feel like you are not what they need? It sounds like you're going through a really tough time emotionally, you are questioning yourself which seems to be causing a lot of grief for yourself so I would like to offer some comfort in asking, are you being too hard on yourself? It's easy to look at all the things that we're doing wrong and to criticise ourselves but please look at all the things you're doing right! Are you children clothed, fed, warm, safe, loved? Then you're doing a darn good job in my books. It seems like you have recognised a need for change with who you are as a husband and as a father. That is the first step to change. Now you need to look at where you think you need to make changes and begin that process - small steps.
Please be kinder to yourself, I hope you're ok.