@kels123, he's cluster feeding because of a growth spurt. Let him eat when he wants because that's what increases your milk! It will pass, I promise.

I'm strictly breast milk but he seems to want to eat every five minutes

Never! Formula and breastmilk is all baby needs for the first 6 months. It will cause gut rot if given too early and rice isn't necessary since it has no nutritional value. if you have reflux issues, there are formulas that have a thickening agent already.