How long does Azathioprine stay in the body if it's not metabolized?

I was on Prednisone 10 mg a day for over 10 years without a problem for Sjogren's Syndrome. Then my rheumatologist retired and my new one wanted me off the Prednisone and on Azathioprine 100mg a day. After six months, my neutrophils came back at 0.7. Reds cells and platelets were also done. I received a call to stop the Azathioprine immediately and to call a hematologist. So far I've have reams of further blood tests, a CT scan of chest, abdomen and pelvis with barium contrast and twice I've been scheduled for a bone marrow biopsy/aspiration, but due to their scheduling errors I'm still waiting. (Have to wait three more weeks now.) I've exhausted, sleep a lot, have abdominal tenderness and outright pain, and have lost over 70 lbs. without trying. I'm having trouble keeping weight on. Since all this started I've been doing a lot more reading on Azathioprine and saw that I missed a few things when I first started it. Namely, that "a measurement of TPMT activity should be assessed prior to commencing the treatment of patients with Azathioprine." (Wikipedia) So my main question for you nice people is how long does Azathioprine stay in the body if it's not metabolized? I did see that it can be dialyzed off. I haven't had any blood work in 8 weeks. Hopefully all of this is due to the drug and not something far worse like cancer, because that means I can recover over time...I think. My current, tenuous diagnosis is pancytopenia.