What Causes Low WBC Level?

Hello, I have been progressively getting sicker over the past 8 months since a rotator cuff injury where the subscapularis was full of toothpaste like calcium, supraspinatus has a 1 cm transverse tear in the centre & the bursa is full of fluid. 1 week ago I had a radionuclide bone scan show low grade active arthropathy in the glenohumeral joint. I have dizziness, fevers, nausea, pain in my hip and shoulder joints, achey all over at times, extreme tiredness, very foggy, can't focus well, red skin rash every now and then & flu like symptoms. I have been tested for everything under the sun for my low WBC, recently I had a Short Synecthen Test and it came back negative for Addison's, my specialist thinks I may have CRPS & FM but they do not explain the low WBC, do you have any idea what it may be? Thank you :)