What is wrong with my baby?!?!?!?

Hes 6 weeks old, they have him on Zantac because they think he has reflux. however its not helping. He cries because hes in so much pain. He eats all the time, like hes not getting full, Hes always moving he cannot sit still. Hes really jerky i dont understand whats wrong with him. Hes on Similac Alimentum. Do you think he could have an allergy to cows milk? What should i do? What could it be? Im taking him to the ER tonight to get some answers or something. Ive had him to just about every pediatrician here in town and still they think nothing of it. My hubby and i between us have raised 4 babies (this is our fifth) and we know this isnt normal. He shouldnt be in this much pain. He doesnt even sleep anymore. Help me!!