Oh candy. If I could make you a stiff drink/hot chocolate and wrap you up in a duvet right now, that's exactly what I'd do.
It does sound as though you need some more time away from work so I'm glad you're going to stay away for a while.
Grief is utterly exhausting (and I hadn't realised you're a new mum too- what an insane roller coaster you must have been on this last year).
All that absent-mindedness and forgetfulness...all of that is very normal (or at least it happened to me too, so I assume it's normal). The description of grief as a 'fog' is, I find, very accurate. Difficulty concentrating, feeling confused and disorientated... all very normal.
Be really, really kind to yourself. Grief is a tremendous emotional AND physical shock. Illness is very common in the recently bereaved, so try to do your best to look after your basic needs- sleep, good food, getting outside, a bit of exercise..... If you can find the time and the energy to attend to those needs, it will help a little.
Thinking of you.