Hey there Mr. V,
I hear you. Sounds like today is an especially tough day, huh? I was having similar thoughts last night, the traditional "date night" and I have nobody in my life either, and dunno whether I choose the wrong types to like or I choose the right types and then mess it up with my issues?
Life can be very difficult, huh? Sounds like you've done many things to address your concerns, do you mind if I ask if you're seeing a therapist? Like anything, some are better than others. My daughter's mother in law in Boston was a therapist for years, and once she and I had a chat about my feelings (similar to yours) and she told me that after 4 appointments with a therapist a person will know if that therapist is right for them. If you haven't found a good therapist to talk to, that might help.
Hang in there. And in the meantime, give yourself some Self Love. Surely there are some things about your character that are admirable. What are they? Make a list and read the darn thing everyday. Maybe you're thoughtful. Maybe you're patient. Those are great traits. I'm sure you have good qualities. Don't ignore them.
Sending you hugs and support,

Anne