Hi..
You can store expressed breast milk at room temperature for 2 3 hours in summers and 6 in winters.
In fridge, it will be ok for 12 hours, best is to express for atleast 6 - 8 times in a day and keep storing milk in bottles or sterilised containers with labels of date and time. The milk expressed first must be used first and vice Versa.
Milk thawed once must not be refrigerated again.
Next Steps
for any further issues, can take online consult. I am a certified lactation consultant.
if it's possible for you, best is to give direct breastfeed rather than ebm by bottle or katori..
katori spoon feed is better than bottle feed any day