It sure sounds like anxiety to me.
Can it be so severe that you cant work or function
Yes it can. Since all of your medical tests came out fine, I do believe this is anxiety. Have you thought about therapy? There are meds to help but, I always recommend trying therapy first to get to the root of the anxiety.
I was very agitated the other day. I felt like I couldnt rest or even sit down. The night I had last night reminded me of your screaming night. I didnt get up screaming but I felt lost and terrified. I even purposely brought on a fear attack to observe the symptoms and try to control it.
Well I didnt go insane but i sure was scared to death and frightful about going to work the next day.