I am sorry you are in this situation. In my personal opinion no one is obligated to date anyone else regardless if he has mental illness or not. We are free to choose who to date. He isn’t your child or your parent or your brother, we do not choose family members. We do choose who to be romantic with and he doesn’t sound like appropriate partner. I understand you feel bad but it’s time to get out and move on. Good luck, you can do it.