I've had a very similar negative reaction at times in waves maybe an hour long, though the general sense of doom tended to condense into very specific ideas: the sort of thoughts you might find when watching a horror movie, except applied to real life and impossible to ignore. As a result, despite having a legitimate prescription, I'm very sparing in my use.

I don't get the euphoria and I avoid using it while seriously sleep deprived - I despise the feeling of my physical body needing sleep. For reference, aside from caffeine and alcohol, it's the only (mind-altering) drug I've ever taken, so it's not due to interactions outside that sphere.