Low WBC count

I had PCP appointment last week and I just got a card in the mail. It said that my white blood cell count was low and the Dr wants to check it out again in a month. The same thing happened 14 months ago and the Dr explained it away by saying that my body was just reeling from the rapid weight loss and was taking time making adjustments. I would think after 2 years though that my body would have cought up by now. Anyone else have this issue? Any one know how serious a complication this is? Thanks. George