I'm so sorry OP - I can totally relate to everything you've posted, and I have nothing but sympathy - especially on this shitty day.
I'm impressed with all that you've done to try to improve and I can't help but feel like those might be things that have changed. Self improvement is commendable one of the most difficult things any of us can do.
I don't want to solutionize, but I'd hate to just post hollow words and leaving you to it. Plus I'm a total hypocrite cos I don't follow my own advice, and I'm the last person who should give advice about this relationships, buuuut...
Dating is largely about numbers and the more people you meet the more likely you are to find a connection. There are loads of reasons why people might click or not, and attractiveness is just one of them.
I wonder if you, like me, are putting too much emphasis on your appearance. I mean, I get it - it totally sucks feeling ugly and its 10x worse when other people make us feel that way. However, ugly people get dates and find relationships and get married and so on... there could be another explanation for why you're still single.
It sounds like you've put a good deal of work into improvement "out there", but how about inside? How is your relationship to yourself?
I really hate that BS about "you have to love yourself before anyone else can love you" because its super unhelpful and makes it sound like we're trapped being lonely forever. Of course it comes with the caveat that a relationship wont magically fix you, but I'll give the benefit of the doubt that I suspect you know that already.
I shouldn't project my own issues onto you, but its not uncommon for fear of rejection to hold us back, or for us to feel unworthy of love or affection because of past experiences.
Sorry I hope this helpful and not totally off-base.
I know its not what you meant, but I like you OP, and really hope that life is kind to you and that you find what you're looking for.