Do they really hate me?
Do you think they have reasons for them to hate you?
I do not have any specific reasons. I only want to ask.
Self-esteem problems are quite common, and you're not the only one. But it's really bad to assume that everyone hates you just because, that is irrational and may become a self fulfilling  prophecy. So, just don't think that and let their actions and words take charge instead.
I want to get to the bottom of it, I want to know if my assumptions are correct
I feel like you're only going to set yourself up for disappointment if you constantly think that people hate you, as you might end up confirming things you suspect by acting the way that you do to make them hate you. I hope you just be yourself and act accordingly towards your values with respect and discipline, so that you don't get hated on and have meaningful relationships with others.