How do I regain ability to multi-task (do more than 1 thing in a DAY)?

I am 2 months on a new med and this one is finally working, putting an end to a year of rapid cycling and 3 hospital stays and 2 attempts.

I can literally only do 1 thing a day. So most days I just work. And then on off days I watch something OR exercise OR do chores.

I used to be a reader. And a writer. And go to the gym before or after work.

I feel like I have a one track mind to the extreme. Is it just a waiting game? When do I stop being so dumb?