Spit. Up. And Poo.

Does anyone else’s little one spit up A LOT? My 3 1/2 month old, who I breast feed, spits up quite a bit. He is gaining weight and he’s a happy little fella for the most part but he spits up so much throughout the day. I have to warn people before they hold him. He also seems to poop often. 3-4 times a day. I can hear his little tummy rumbling sometimes, I just Worry he’s uncomfortable. Any thoughts?