Burning out?

Usually this feeling only lasts a few days, but for at least two weeks now I've just felt completely dead. Today I have done almost literally nothing, although I did hoover, and hoovering is something. I ate crisps, biscuits and cranberries, drank some water, had a cup of coffee, watched daytime TV, got frustrated that ITV have started chopping up episodes of Morse and Poirot and spreading them over two days, etc. I have a head that feels like it's full of lead, cannot muster any motivation to do anything, and feel very much at home curled up on the sofa hiding within my nice khaki-coloured hoodie. There is no end in sight, even though I've got loads of things to do.

Any suggestions, folks?