Hi Smigger, i can relate to how you feel also, i get this way quite often, i am normally fine first thing, then i take all my meds like a good boy and POW, as they start to kick in i can feel myself becoming depressed, have no enthusiasm for anything, no shops, dont want to get dressed, go out, nothing, and before i know it the day has gone.
Mine is all down to the mixture of pills, i have to take my insulin my metformin, glictazide, and other diabeties medication and also my heart pills, angina pills, BP pills, i am certain it is the 40mg of isosorbide that is doing this to me.
Maybe it is your pills also, please see your GP, you might have already done so already, i know how you feel and it is horrible.
What helped a lot was my doc changing my 800mg metformin pills to 500mg SR pills, this helped a lot, i noticed a difference very quickly.