is your son teething by any chance? many times, babies around this age suffer from loose motions as they start to teeth. the reason is that in a bid to ease their discomfort and pain in the gums, they try biting anything that they can find. i would suggest feed your baby curd rice and also make sure he is properly hydrated. you can give regular water, tender coconut water, lassi and so on. also, do speak to the doctor and be extra careful that he does not pick up something from the floor and puts in his mouth.