Overfeeding?

How many ounces are your babes getting? My son gets 6oz every bottle almost every 3-4 hours. Sometimes he gets 30oz a day sometimes 36oz , sometimes even more like 40:( I feel like I’m overfeeding him but idk what’s the propsr amount. I noticed he’s been spitting up a lot recently , and I think it’s cause hes getting this much milk plus solid food on top of it and it might be to much for his belly. So now I’m thinking on just doing demand feeding instead of following a set schedule for bottles? Would that be bad? Any thoughts? Any ideas on how to try and help his spitting up problem. I feel like I’m just failing at everything lately.