It sounds very panic attacky certainly! You said it wasnt but honestly that sounds like a poetic description of a panic attack. You know you best, but a panic attack definitely doesnt have to be triggered by something scary or shocking - Ive had some come literally out of nowhere (well... I had had a lot of caffeine lol)
Ive never had that or heard of it otherwise. When Ive been very clinically depressed before I took Effexor, for me it was more like lethargic and having a hard time switching tasks. Ive definitely felt hopeless or felt despair, but I wouldnt have described it the way you wrote just now.