Am I beautiful or useable

I hate writing about negative things, I am afraid of sounding whiny. But I am really confused. And I have no one that I feel i could vent to or give me unbiased advice. I have been in relationships with so many people who actually virtually the same. At first they are sweet and I see their potential. Then as time goes on they show me their real self, all their issues and flaws. This wouldn’t be a problem in a normal relationship. However why do these people always show me just how fucked up they can be. Is it my fault? I don’t want to think so but I have heard the phrase “you teach people how to treat you.” Why are my feelings so  insignificant when they aren’t useful. Why do they get to take out all their negative emotions at my expense. If I leave it will just happen again. And I would have less money. I would go back to my parents who do the exact same thing to me. I just want to go sleep.