milk had weird smell in fridge after 2 days

kuipo324

ive been pumping 2oz every morning, and then combining it with the pumped milk from the day prior so i can freeze 4oz. (this way i always have 4oz of fresh in the fridge) i noticed today when i smelled the one i pumped 3 days ago, it had a strange smell to it. i tasted it and it tasted kind of weird. not sour, just off. is it just because its a few days old? im worried now because ive never really checked the smell or taste before i go to freeze it. how do i know if i defrost it if its bad or not? i thought it was totally fine to leave it in the fridge a couple days before you freeze it. should i not be doing this? i wonder can it make her sick?