My situation sounds similar to Nanners' situation, except that lately, I feel so tired when I wake up, too. I am normally a morning person, but when I've been waking up for work, I feel like I haven't slept much, even though I normally get 9 hrs/night. It gets a little better once I get up and gets the joints moving, but then it starts to get worse again as the day progresses. I'm so tired after work that I often take a nap and then go to bed a couple of hours later for 9 hrs.
My last blood work was fine, as far as I know, and I've never had problems with B12 or iron before (except after prepping for a colonoscopy - iron was low). My Crohn's is in remission as well, but the arthritis is very bad right now. My rheumy reduced my work schedule for 2 months (which is over after next week), but I'm still working a few full days each week and those days wear me out. I wish I had an answer for you but I don't...but you aren't alone.