i dont know whts my problem

thanls for ur suggession fnd.but i m having this habit since i my childhood.i m not tht old too to have this.really saying my prob is different.whn my parents see this .whn thy see my condition thy cant immagin how do i manage to b in a state which is even difficult for a general or normal person to do.i mean impossible for a person.its not due to automatic trembling.rather whn i get some unusual things in my mind or some sensations in my few body parts,i automatically driven for moving my legs along with whole body sitting on bed corner with my legs in hanging position.i apply max force to move my legs n body too.but couldnt realize at tht time.later whn get satishfied with this act i cool down n fill lot of pain in my body..i was not able to explain my prob completely n perfectly.sorry for tht.