I feel like nothing is working for my son. He keeps having constipation. His poops always a dark…

I feel like nothing is working for my son. He keeps having constipation. His poops always a dark color and sometimes he will have balls of turd.😔 we had X-rays seeing if there a blockage but the doctor told us that there wasn't. We have changed his formula so many times I just want my little boy better already. He's been dealing with this ever since he was born.