I'm so sorry you are in this difficult place.

But I know how you feel. I'm old now... too old. And, looking back, I also hate (almost) every decision I ever made. Even the few decisions I made that turned out to be good ones came on the heels of some bad decision I regret. And the reality is there's nothing I can do about any of it now. Plus, I often think I'm still making bad decisions. They're just smaller ones due to the fact my world has become so much smaller as I've aged.
I'm glad you're in therapy. I hope you find it to be of benefit. I'm not in therapy. I think about it once in a while. But the reality is it wouldn't change a thing at my age. All it would do is cost a bunch of money in an effort to die happy... or at least a wee bit less sad. I can't justify it.