Hi Laura,
I agree with the previous poster that you should check with your doctor. Extreme fussiness and excessive gas are common sypmtoms of a milk protien intolerance, so your LO could be reacting to the formula. You may need a more specialized formula such a hydrolysate formula (which means that the milk protiens are only partially broken down) or an amino-acid based formula (where the protiens are completely broken down to free amino acids making it easy to digest).
Also, if you do switch formulas it may take up to two weeks for your LO to get rid of the other formula completely, so you should give the switch a fair try.
Is your LO showing any signs of reflux? I hope it gets better for you soon.
Rachel
Mom to 2 boys
Augustboy02 - Sensational Sensory Kid
Decemberboy04 - former reflux baby