My doctor rang me today say i have a low white blood cells what could this mean?

Many possibles: It could mean you had a recent viral illness, or it could mean your immune system is struggling for some reason right now, it could be your normal or it could be a more serious disease. Isolated numbers don't mean anything. Must be taken in context of other symptoms and why it was checked in the first place, and is just one piece of a puzzle in figuring out what is going on with you.