Her crate is the smallest size (shes 4 lbs.) and i let her outside before bed but it seems no matter how long she is playing out there (5 minutes or 25 minutes) she doesnt go #2

she never used to go in her crate until recently, i blamed the first couple times on maybe her stomach hurting but its becoming a regular routine and after she goes she whines and whines until i wake up and clean her crate in the middle of the night. She doesnt even whine before she has to go, she just goes and then whines after! its so frustrating