I have chronic fatigue syndrome and several other chronic illnesses that cause fatigue, so I've got some experience here. I've had some luck with indicas, if I'm lucky a couple puffs can help me stand up long enough to shower. Using more than that rarely helps me and tends to make things worse. I've had the best luck with green crack, but I haven't tried a whole lot of strains for fatigue.
Amphetamines, Ritalin/Concerta, or Nuvigil/Provigil might help you much more than cannabis - in my case stimulants tend to make me jittery and the crash can worsen my other issues, but they definitely give energy. Obviously be careful with that stuff, particularly speed and Ritalin.
If you don't already know the root cause of the fatigue, I'd also encourage you to look into possible conditions yourself, in my experience very, very few doctors are competent with chronic fatigue issues. Talk to your doc about a test for active eppstein-barr virus and cytomegalovirus (those probably aren't direct causes since your fatigue has lasted so long, but they can be indicative of chronic fatigue syndrome), and get tested for all the following if you haven't already: rheumatoid arthritis, lupus, multiple sclerosis, lyme disease, celiac disease, non-celiac gluten sensitivity, hypothyroidism, and fibromyalgia. That's just the stuff I can remember of course, I'm sure there's more. There's not really any test for chronic fatigue syndrome, but if all of those other tests come back negative that's probably the diagnosis you'll get. And of course if you already know what's causing it, you can ignore this paragraph.
I hope you figure out a way to treat your fatigue!