I dont really know how to explain it... it's like this huge wave of emotion over takes me, and I can physically feel it in my muscles. I have the urge to lash out and brutally hurt myself. Bash my face, jump out of vehicles etc. But instead I find my muscles locking up. Sometimes I rock in place unable to move, moaning or howling. Other times I cant sit still due to the distress yet I have little control over my body. My limbs contort. Even my fingers, and I throw myself around the room, flopping about. I've never heard of any one experiencing anything like this... 
I've had bouts of extreme dissociation, and seizures caused by stress. This seems to have taken the place of that.. 
Does anyone experience similar or know if theres a name for this? TIA