Baby didn’t want pumped milk

Hi everyone, I pumped 2 days ago in the morning and then yesterday evening we tried to feed him with pumped milk. He ate about 20 ml out of 60 ml and it seemed like he didn’t like the taste. I pumped fresh milk and he took it. I don’t know why. Usually I breastfeed him directly but sometimes we give him bottle if he has tummy issues and he wouldn’t latch. Afterwards he latched and relaxed. I put the milk in the back in refrigerator and it was closed with cap. No way it would spoil! And I didn’t eat anything weird that day and nursed him all day so I don’t know why he wouldn’t take the pumped milk. He’s only 3.5 months old and we fear that maybe his teeth are starting to bother him (Drools a lot, obsessed with sucking his fists, latches a little bit differently). The milk had that separation of fat and after warming it it was all mixed up. Does the separation happen with refrigerated milk too or only with frozen milk? Thanks