What Causes Persistent Fatigue?

I was in the hospital for a week in March due what I was diagnosed a few years ago, crohnes disease. I have had increased fatigue (NOT JUST TIRED....I literally fall asleep at my desk sitting up....), I have NOT lost any weight, I have pains in the middle of my stomach right under my rib cage and they just did a colonoscopy two days ago taking 4 samples and removing a polyp. What could be going on???? I am 45 years old and have a history of my paternal grandmother having colon polyps, but I don t know much more. I do have arthritis (psoriatic and they also said rheumatoid). The lowest vertebrae in my back only has about an eighth of an inch cushion between the two from xrays (I have had a vertebrae shaved due to a buldging disc in 2009 after a chiropractic appt.) I was told by my doctor to take liquid B vitamins (Under the tongue because the intestine do not absorp it fast enough. Please help me, I am afraid I will loose my job.