Son has low white blood cells

My son seems to be sick all the time. He goes weeks at the time eating very very little. He is 23 months and complains that different areas of his body hurt. He has strange fevers that come on suddenly and go away within hours. He vomits occasionally out of the blue or in his sleep. I recently had to get firm with his doctor and had him do a urinalysis and CBC. Urinalysis came back with high ketone levels and CBC results said he has extremely scary low white blood cell count. We are going tomorrow to have a full chemistry done. But in the meantime does anyone know what these symptoms fit?