Where is my coolant going?

Hello I have a problem, My women95 Grs and Am GTCP has a mysterious problem. During the corse of a week and a half the thing has gone through almost 1 and a half gallons of coolant with no apparent leak ( I looked everywhere ) I also checked the oil..nothing just oil..does anyone know where her coolant is going??

check by the water pump when the water pump goes out there is a weep hole that lets coolant out while u drive or have the car off

This might also be the heater core. There is a drain on the firewall, might be hard to see but your coolant will drain while driving.