Acid Reflux/Formula Help

Hi everyone!  I am just reaching out to see if anyone has advice or similar situation to mine.  I have a daughter who will be 2 March 1st and she was breastfed until 6 months and never had any reflux issues and has always just been easy going with whatever we did that was new (breastmilk to formula, solid foods, using a sippy cup, etc.), and so now I have my son who is 4 months today and it is a whole different story.  He was about 4 weeks early (she was just about 3) and had some issues at first but is doing well now health wise and growing very quickly, but I am kind of at a loss with trying to figure out if I should be doing anything differently.  I could only breastfeed for the first 2 months and went back to work and wasn't able to keep up with pumping so he went on to formula.  So basically, I feel a little clueless about what is typical for formula fed babies, in particular ones with reflux.  My worry is that he takes about 2 hours to finish a 4 oz bottle (and sometimes not even that and I have to waste the rest of the formula) and so I did reach out to my pediatrician and they suggested adding rice cereal to his bottle and I did that for a few days and the first day seemed great- he actually slept fairly well and then the next day it was almost like he wasn't very hungry all day long and the next day he seemed uncomfortable.