1998 Subaru Legacy overheating

HI, my car is overheating, I already change the thermostat and the radiator. My antifreeze is runing out to quickly every 2 days, the heater some time works and some not, I have a check engine light po325, I do no see water in the oil.

it' s overheating a 7 milles.

some pepple tell me that is the water pump
and others head gasket
hte car is working fine, no low power

thank you