Every little insult or minor inconvenience seems to send me into a spiral of self-hatred and that makes me angry at myself which makes me feel like crap. Every time this happens I start calling myself worthless, useless, even selfish on some occasions. What is so wrong with me that I’m so weak? All I ever wanted was to be strong and to helpful to other people. I want to be happy like I was when I was a kid. Why the heck do I have to be so fragile!?

I'm sorry not much for words of wisdom, but I understand how you feel I feel the exact same a lot of the time too

Same. Self pity is a monster.

I guess you're dissatisfied with life in general.
If you had a hobby or anything you were proud of, you wouldn't feel useless and worthless, for you knew you aren't.
Make something out of your life and you will develop a sense of self-worth.
Stop that attitude of self-pity and try to develop a significant personality and your problem will vanish once and for all.

https://youtu.be/tJixs2FoZ_Y

You can never make everyone happy or be liked by everyone. There are always people who will insult you or treat you bad. Stop letting them get t8 you since they don't even know you and f em, you're imperfections is what makes you unique too. Everyone has imperfections, and some people can't stand them and will tell you, but they forget they have their own lol.