I agree with TheatreKid - this sounds more like anxiety to me, or at least in my mind it is one of the defining characteristics of anxiety...though it seems to get ramped up when high or doomsday-esque when depressed, at least for me. I also read that there is a definite link between bipolar and OCD (meaning that if you have bipolar you are more likely to also have OCD...or maybe it was the other way around?)

over-analyzing is one of my main issues, as it usually leads to rapid-fire nonsense (as when I found myself showering at 4 AM the other week while philosophizing about how a dissertation is exactly like a loaf of bread...)