Spit up

My little guy is starting to spit up quite a bit but I don’t know why. I burp him after a few minutes and after he’s done eating then keep him upright for a few minutes. He’s mainly doing it at night when he’s in his pack and play, I noticed the little spit up stains today. I feel bad I haven’t noticed he’s been going through it for a few nights 😰 he’s exclusively breast fed, minus an occasional pumped bottle but that’s only if we’re out and about or dad forces me to nap. My mom said he might be getting too full but don’t babies usually know they’re full when they’re drinking right from the tap? Any advice or thoughts?