Are you under the doctor at the moment re coming off pregabalin. You don’t have to white knuckle it surely?

About the job, it’s up to you how you feel but from what you’ve said it sounds like you have a good case for unfair dismissal.
Try and eat some food thats easy to swallow. Custards, yoghurts, soups. Even high calorie Complan.
Get up and shower but don’t go back to bed. Go outside into the world, just for short walks at first. Maybe look at some mindfulness. Terry did a brilliant post some years back listing lots of resources.