I've had "off" white cell counts, too, in the past year. My WBC has been low, my lymphocytes HIGH, and my neutrophils low. I'll get it rechecked and they're all normal, then next time "off" again. It scared me because my dad died 18 years ago of leukemia (at age 76- I'm 56).
I have decided it is from having Hashimotos. I think I remember reading autoimmune disease can affect your white blood cell counts. So I've quit worrying about it.