Make sure you have bloods done and check if anaemic post surgery or ensure no thyroid issyes which can contribute . I also needed a multivitamin despite a good diet as my body was depleted from chemo and surgery.
I had to pace myself. I'd have a short nap when I got home from work so I could get tea prepped.
I increased exercise very slowly and found if I overdid it I'd crash in a couple of weeks. I still have to pace myself 3 years on. It's just the way it is.
I found a short walk at lunch helped also. Breaking exercise up seemed to work better.