When on mtx I often had low white blood count. It can suggest infection so my advice would be healthy diet, healthy life style. If you need supplements take them but if your diet is balanced you should get what you need from your food. Interestingly since stopping mtx bloods have all returned to normal except ESR and CRP (Inflammation markers)

Oh Nasty, I would see a hematologist they know more about blood than any other doctor ever dreamed of.