I am also feeling flat - but a 2 day hangover is to be expected I reckon
I'm not expecting to feel any better tomorrow either. I'm hoping Thursday brings improvement.
Have you tried some Epson salts in a nice warm bath??
I find it helps with the recovery - drink lots of water during and after the bath to help flush the body.
You can buy huge bags of Epson salts (5kg I think) from Boots - don't buy the small packs they use for internal purposes - will cost a fortune!