Spit up

Why would my baby randomly start spitting up almost every feed? LO is 15 weeks and never really much of a spit upper before. Occasionally but very random and liquidey.

This week he started spitting up immediately after most every feed and it’s thick and chunky and smells like vomit. No temperature or any other symptoms.

I also noticed my shirt when I leak smells like vomit which isn’t usually the case. Normally I leak all the time a little and my shirt dries and it’s never an issue but this smell is obviously different