No help to you, but just wanted to confirm that fatigue is a very common feature of MS and being knackered by mid-afternoon isn’t at all unusual.
Not a cure, but a lot of folk have a short nap in the afternoon to help ‘recharge the batteries’ a bit. Helps a bit, certainly. The only other thing I understand that may be beneficial is vitamin B12 supplementation …sincerely hope someone will be along shortly to advise further about possible ways to increase energy levels ?!!
I myself often need a short kip by mid-afternoon without doing anything physically strenuous despite a very active background (…used to play Saturday & Sunday football, weight-train 3-times per week and swim at least once every other week).
Just one of the many things we find a way of coping with.
With best wishes,