Meyers Cocktail (excuse my spelling)
Fatigue and vitamins are absolutely related but it is so complex I just leave that up to my natuopathic doctor to figure out. B12 should give you energy and Vitamin C is great but the only downfall is if you have it is excess it can cause diahrea which loses nuturients from the body. There are so so many vitamins and minerals that we need the you could very well be deficient in other vitamins or minerals. I would start by getting a Vitamin D test done by a doctor or naturopathic doctor and I would recommend getting a Meyers coctail vitamin injection done by a health doctor. You can check out the website just search "Meyers coctail" vitamin injection so you can read about it first. It could very well help you out a great deal.
I hope I have been able to share something helpfull here.
Good Luck