What should I do if family falsely claims mental illness?

My family members are defaming me and threatening to declare me mentally unstable so they can send me to a mental asylum and claim it’s inherited. My father even told my mother to pretend to be mentally ill in court to support this claim. They are constantly bullying me, and I feel helpless, as no one around me is helping. I suspect they are spreading my photos along with false information, but I’m not fully aware of the details. I’m afraid to go to the police because my father threatened to throw me out and cut off financial support. Please advise what I can legally do to protect myself in this situation.