Crushing fatigue is awful! Most of us experience it whether it's only during a flare or all the time.
Both Snoopy and NurseNancy gave some great advice. I would add in maybe taking some vitamin B12 or a B complex to see if that helps. Check with your doctor first as he/she may want to run a blood test for you B's first to see what your levels are.
I hope you start feeling more awake and rested soon.