What Causes My Infant To Cries Often And Refuse To Drink Milk Properly Despite Using Aptamil Gold 1 And Colicaid Drops?

My son is 3.5 months old and is totally on formula feed. He keeps crying most of the time and doesn t drink milk properly. I give him colicaid drops twice daily but doesn t seem to help. Please suggest what should I do? Should I change the drops or what? I am using Aptamil gold 1 formula feed . Please suggest which formula should I use?