My Cocker had the same problem. I switched her food as well and have finally found one that works. It is called Performatrin Ultra (Chicken & Brown Rice) - It is holistic all natural with no by-products. Similar to the Wellness product but works better for her. This can be found at any Pet Value store. Now she poops exactly twice a day - once in the morning at 8am and once at 6pm.
What are you feeding him? If you're feeding him food that contains corn, then he's going to poop a lot, because corn is just a filler -- it has no nutritional value at all, so they just poop it out. Put him on some GOOD quality food that does not contain corn -- like, Orijen or Taste of the Wild.
My Cocker is 13yrs old.From day one she has always been a pooper. they have special food quite expensive at pet smart. call Banfields pet hosp in pet smart it can only be given by prescription. They don't poop as much while on it.