HELP how do i stop my head shaking?

basically about a year ago or maybe less i realized my head started shaking when i'm on stage. when i have to stand still it's even worse. now i get it just when i know people are watching me i don't even have to be performing and i don't have to be nervous i can feel completely normal and know someones watching me and it starts to shake. my legs and hands also shake and people have actually said to me before like omg your hands were like trembling. it's really annoying cuz people say i'm a really good actress but everytime my performance gets destroyed by the involuntary head shaking thing PLEASE tell me how to stop it it's so humiliating and stops me form doing things it's not like people don't notice, i've tried eating bananas, calming pills, turning my head round and round before a performance and concentrating on another part of my body or moving my toes nothing works. i've even been so nervous i've asked to run away with my friend jst before a performance...HELP