You are not a dirtbag, you're one of the most caring and compassionate people I know. That is not a dirtbag, a dirtbag is a horrible person that cares only for themselves. You're wonderful and deserve to hear that every single day!
Every time he says anything, just keep in mind he's a liar and his words mean nothing. He's just trying to get your attention, and he doesn't deserve any of it. We're here, we love you, and we don't believe a word that he says!
I'm sorry you're still dealing with them, it's no fun having someone close putting you down all the time. That was my mother when I was young, it made life a living hell. I feel your pain, but you e got support and compassion right here!