My 4 month old boy get vaccinated on Wednesday.. He had fever for 2 days.. He drink milk even when he had fever.. For the past two when he is awake he refused to drink milk .. he feels sleepy ... he wants to put him in the cradle to sleep and sucking his thumbs.. I feed him only when he is in deep sleep .. he refused to drink and cried a lot when I put him on my lap to feed.. Is this a major issue???