Bad milk?

Starr • Baby #3 Coming Soon! Selenya Avery born July 2016! 🎀 Angel Baby Lily🌸👼🏼 Secilia Elizabeth born October 2021 🌈💖 Maverick due May 2025 💙
How can you tell if breast milk has soured? My two week old has been a little extra fussy and I'm not sure if it could have anything to do with the milk being in the fridge for the 9th day. Is there a special way to differentiate between still good and too old?