@Toth Woah. I am at a bit of a loose end right now (hence clicking this thread, which I've often been curious about).
I can't begin to imagine what you're going through. That's the thing about this shit - no one can. Even if you've been dealing with this type of thing for 40 years or so, you can isolate factors, engage with therapy; try to eat right, exercise, cut out caffeine, alcohol, nicotine - you name it, and it can bite you all the same. I must stress I don't know your situation, and the last thing I'm trying to do is say, 'there there'. But I feel you. And you're not alone.
I did see you said 'friendless background'? Genuine question here: have you really never had a friend? If so, then I'm not being patronising, but I am straight up your friend. I know that doesn't mean much, as I can't actually help, and we're never likely to meet, but everyone needs a friend. Even if it's just words on a screen.
I know this sounds cliche as hell, but a lot of the cool, together types who are unconsciously excluding you (I honestly can't believe people at a base level are so callous) are like as not feeling things akin to you, albeit to a lesser degree. I don't for one minute suggest human experience can be generalized in such a way, but at the same time, we're not all that different either. Mammals in the space time continuum, dude. Mammals in the STC.
From the above I would guess you are an introvert? Introversion is a wonderful thing, and should be celebrated more - particularly in the bombastic world in which we live. But I suspect you know yourself that it can only take you so far. Please try and speak to one person today, even if it's just a passing comment to a neighbour, or a hello to a guy in a shop. I know this is easier said than done, and is probably a cackhanded piece of advice, but the social skills you think you lack (though I'm guessing from your sensitivity do possess, and just don't feel confident enough to use) will only grow if you're brave enough to exercise them. You got this dude. You really do.
In terms of teaching: I don't know which country your based in, but maybe you can find some sort of web based forum for discussion? I used to teach English to speakers of foreign languages, but I doubt it would be of any use here. Are there any online repositories of tips etc? I can appreciate researching this is a chore in itself - particularly if you're low - but it's something to do at least? If you feel up to it, I would definitely have a look
Anyway, I'll stop bleating on now, but straight up, feel yourself. And thank you for what you wrote. Peace and love.