Breast Milk Turned Bad

I have excess breast milk leaking everyday and need to put on milk collectors to contain leaking milk. After collecting for hours, the milk collected (under humid weather) together with sweat are transferred to the milk bottles immediately used for pumping of breast milk. My newborn drinks it within 24hrs period after the mixed milk is kept in the chill room of the fridge and have very bad tummy ache and loose stools with mucus looking substance. May I know what is the cause of the tummy ache and how can I resolve issues for tummy ache and excess milk storage? So I throw away those milk collected by the milk collectors?#Needadvice #breastmilk #askmommies