I have the same reaction (physical) to a screaming kid. It has made raising my baby incredibly difficult (especially the first year). Mentally, I understand that it's just a crying baby and that's what they do, but physically I was shutting down - body tensing, a surge of extremely stressful energy rushing through my body and ultimately being left unable to function. My wife thought I was nuts and was just faking it. I tried searching for a medical explanation but came up short. The closest I would describe it as something I hear chronic fatigue people say -- not having energy to get up, no matter their mental state. I would sit there, practically paralyzed by stress, or whatever that stress induced.