my baby is 13 months old., I hv been cleaning his tongue since his birth with a soft cotton cloth but now as he's growing older he doesn't let me clean his tongue. he doesn't open his mouth and starts biting when I try to do it.. I hv started giving him formula milk from last 15 days as suggested by his pediatrician and now I can see a white coating on his tongue. really worried what can i do?? how should I clean his tongue??