Taking him off formula would mean putting him directly on cow's milk, and that is NOT a good idea. That's the perfect food for baby cows, not baby humans, who need a different combination of protein, fats and sugars.
Do try other formulas, though. I have heard that Enfamil Gentlease is well-tolerated by many babies that don't do well on other brands. Talk to his doctor about this if you can.
And some babies also suffer from acid reflux, with stomach acid backing up in the throat. Propping him with his head and upper body a little higher might help him feel better.
Be sure to burp him well during and after feeding, whenever he starts to squirm and seem uncomfortable. Rubbing his belly gently or moving is legs like he's riding a bicycle might help him pass gas more easily.
Be sure he's not hungry, too. Is there any possibility he's actually crying for more food? Babies usually go through a growth spurt around 4 months, and they are hungrier.