As soon as they switched to the mixture, constipation started. They us…

As soon as they switched to the mixture, constipation started. They used a enema first, then a nozzle, then Nutrilon Premium and now Nutrilon Comfort, and he can't go potty on his own. We give Dufalac (I'm worried that he can't go by himself (it was thick, now it seems like it's not so thick but still doesn't go (What should I do? I don't know anymore).