Hi T.! Boy i wish my daughter would slow down her eating! haha. My sister's son sounds just like yours - she breastfeeds him, and he probably only shows interest in eating every 5 or 6 hours, and for a 2 month old, that had me worried, but Riley is gaining weight well, hitting his developmental milestones, and the doctor isn't worried. I would not hesitate to express your concerns with the pediatrician, and explicitly state that you're thickening his formula, etc. Some babies (my nephew included) don't respond well to thickened formula- they may find it hard to digest, and if he's got reflux it may actually be hurting his throat when it comes back up. Try experimenting with different formulas- maybe he just doesn't like the taste? In any event, what I've always heard is that babies eat differently, and as long as they are thriving, it's normal for them. :) good luck!