My depression comes and goes in big ways, so much so that I am almost convinced I am bipolar (I'm seeing a therapist in a matter of weeks or even days, so time will tell, though my main concerns are the dillusions I am having). I go from feeling very, very down, much like what you are describing to the point of feeling drugged. Some times I can't even move a muscle and just sit on my floor with my eyes closed. I think those times last an average of two days or so (though I have had it last for weeks at a time), and then I come back to life, which can go to the point of thinking myself superior to everyone around me. I'd say I'm much, much more down than not, and the "highs" last a very short time before I'm slapped back into reality, but I do feel neutral at some times as well.
My most recent down feeling lasted about a day and a half. When I woke up the next day I felt better. But the worst is when it physically affects me like you said. And sometimes nothing can help it, but to try to think positively or to sleep it off.
Have a nice weekend -Ace