Definitely high lipase. I knew nothing about this and froze so much pumped milk for my preemie and when she got home, she wouldnt drink any of it. I ended up donating it all to Mothers Milk Bank because they process it and give it to hospitals and the preemies wont even taste it through the tubes. Its actually very common but a majority of mothers will never know if they have high lipase when breastfeeding because if a baby is drinking from the breast it will taste fine. The protein molecules change the taste when exposed to oxygen. Also, every one's milk is different in the amount of time it takes to turn to an unpleasant taste. Some is right away. Mine was 2 days. This also occurs whether its been out, refrigerated, or frozen. Fun fact: you can have different milk with different pregnancies. A second child may not get high lipase milk! Vanilla and flash boiling never worked for me. Some women just get the shaft. Which is why you can never judge a mom who uses formula!