I feel like a lump too, so you're not the only one. Very lethargic, very apathetic, very blah. It feels more like a physical thing than a mental thing.
I'm going to try a list of 7 things and see what happens. If it makes me feel happier with more energy, will repeat daily and add on...
One thing that will make me laugh, maybe a youtube video of Ed Grimley
One exercise thing, maybe a walk on the beach
One TV show or movie I've wanted to watch
One good deed for someone else
One cooking or craft project
One cd to listen to
One long hot shower
Try to tell yourself this will pass and move through it, from what everyone says here it does come in stages and will rebound.