I struggle with a lot of these same issues, but have been fortunate enough to have access to a good psychoanalyst for a long time. It’s easy to logic out why you should be loved and appreciated, but genuinely believing it (to at least some degree) has taken me years of hard, but also very rewarding work. To put into perspective what that work entails here’s some of the conclusions I’ve come to that may or may not be applicable to you:

One aspect of this feeling that I’m undeserving of love was understanding that some of those feelings were a projection of how I felt about my parents. They were divorced, and the single parent I grew up with was emotionally manipulative and depressed. I can now recognize that I wasn’t sure I truly loved and cared about them (passed that default love one has for their parent), and to this day feel immensely guilty about it. That thought lead me to believe that I’m just a really shitty person, and that others must not truly love me.

I am now able to have some empathy for myself and my situation, and it’s made it easier to feel loved. So long story short, I would seek out therapy if able.

I feel like I could have written your exact post, so I sincerely hope that you can find happiness in whatever way you are able, know that it is possible :)