How much spit up is to much spit up!?

Caitlin

My son just turned 4 months and is strictly breast fed and for the last month he’s been spitting up quite a bit, he spits up little bits sometimes and other times is a lot, and he could spit up right after a feeding or half hour after to 2 hours after, he’s gaining weight perfectly and is very happy even after he spits up, what do you mommy’s think?