What you wrote is pretty-much exactly where I'm at to a large extent. (Oh... & by the way... I don't know to what extent you're hitting your head against things. But take it from me it's a very bad idea!) I don't know what mistakes you've made of course. My personal perspective is that there are some things one simply cannot forgive oneself for. That's where I'm at personally. So what I strive for is simple acceptance. I am the person I am & I did what I did. That's it.

I know you mentioned you've tried meditation & it didn't stick the way you want it to. But there's more to it than simply following your breath, or whatever technique it is you've tried. My personal perspective is that there aren't any great answers to these kinds of problems... no magic solutions you just happen to have not heard of before... & once you find it all will be well. I wish there were!

For my money, as the saying goes, if one is looking for techniques for achieving self-forgiveness or even just what I refer to as simple acceptance, there is no better resource on this earth than the book: Start Where You Are- A Guide to Compassionate Living by the American Buddhist nun Pema Chödrön (Shambhala Publications.) As Ani Pema writes in this book... you can imagine you are the worst person in the world. That's a great place to start! But you can't just get a copy of the book from the library or wherever, read it & set it aside. You have to read it over-&-over. Underline significant passages. Dog-ear important pages. Keep going through it until it falls apart in your hands! Practice the various techniques. (One doesn't have to be a Buddhist to do it.) It's not a miracle cure. But, over time, I believe it can help you to get to where you want to go better than anything else I know of. I wish you well...