Interesting thread and have enjoyed reading the comments on here.

To the OP, you remind me a lot of someone I used to know. I hope this doesn't sound judgmental as is merely an observation but you seem to have a great deal of hostility towards people who you seem to say have failed you or let you down by not being your friend or not going out with you when you want. You may think you hide that hostility but it can show despite the best of efforts and may be one of the things people find off putting.

If it becomes clear someone doesn't want to hang out with you or even if they do but just not right now, then you need to learn to forget that and move on. Obsessing over the reasons why is going to drag you down. You'll never really know why - you may have caught them at a bad moment, they may be doing something else with established friends, they may just not want to spend time with you. Or, as others have said they could have their own issues, suffer from anxiety, be insecure about you or how you think about them. One thing I've learned is that a lot of people suffer from anxiety and depression and hide it well. They may seem very sociable with their longstanding friends but those will be the result of possibly years of building trust. These people don't know you yet - it takes time for some people to feel comfortable with friends so just because they seem hesitant at first, doesn't mean things couldn't develop over longer periods - years maybe. So perhaps look at the bigger picture if you're able. And don't be too intense too soon as that could scare potential friends away.

As others have said, neediness is off putting. If someone doesn't respond to a text and it's someone you don't know well / have just met, it is going to be a red flag to them if you chase them up or get annoyed with them. The hard truth is they don't owe you anything, nobody does. And even if you get someone's phone number or they go out with you once or twice, it still doesn't mean you're necessarily going to be close friends. Nothing is guaranteed so learning to live with the uncertainty is another good skill.

And you do seem to be putting the focus of your self worth onto other people. You'll never really understand them, it's all theory. Why not concentrate for now on getting to know yourself. Do something non social for you - start a correspondence course, read the complete works of Shakespeare, take a car maintenance course. Anything that doesn't provide you with the opportunity to confirm your own negative social beliefs but instead gives you a sense of personal achievement.

As always, I often find it hard to follow my own advice but I do genuinely believe all the above and do attempt to put it into practice and things aren't as bad for me socially as they used to be. And I certainly feel better about myself by not focusing on others quite so much and instead getting to know myself.