Loose motions. Reduce his loose motions!

My son is 4months 15days old now,he is a bottle feeder,from past 1week he is suffering from loose motions,we took him to doctor and doctor said because of indigestion gave us a medicine n injections for 3days after that they admitted him in hospital and even saline was injected even then his loose motions did not come to control,after that we took him to another doctor he changed the milk powder lactose free powder n loose motions control feeding powder,and gave us some medicines for 3days,even now his loose motions did not come to control.we are very much worried about our child we changed 2doctors and tried different medicines suggested by them even the motions did not come to control,he is taking feeding at the same time he is getting loose motions. Poss suggest how can we reduce his loose motions