The right side of my son's neck is swollen, he has a headache and low grade fever. cbc showed elevated wbc and low lymph.

Likely strep i: did he have a throat culture done. It sounds like he had a strep infection. Headaches and enlarged lymph nodes are common symptoms as well as abdominal pain or sandpaper rash can be symptoms as well. Low lymphocytes in the face of elevated total white blood cells leads one to believe it is a bacterial infection and not viral like mononucleosis.