My son is 4 weeks old, and Iv had to change his milk as he was on cow and gate but wasn't working out for him, was very constipated.. so he's now been on mamia first milk for a week and he's still very constipated, been given tablets to place up his bottom to help him poo but they are the only things that actually get him to poo :( and when he does, the poo is really hard, really green and he really struggles to get it out. Takes a good 10 minutes for him. What shall I do? Any suggestions? Shall I change his milk again?