I have a problem with my radiator and antifreeze, What could be the problem?

Hi guys I have a Honda civic lx 97, I bought about 7 months ago, since then I have bought a new radiator because the old one had a huge leaking problem, anyways I never new How long a gallon of antifreeze could last me. I now know I use too much (I've bought two gallons once the first time i changed the radiator, again today[spand time of 4 months]) antifreeze I don't see any leakage, what could the problem be?

If the coolant is not leaking out, from the radiator, the water pump, or a hose, then it must be going out through the exhaust. Probably a blown head gasket.

Rent or buy a cooling system pressure tester and test for leaks. You have to remove the thermostat (reinstalling the thermostat housing) and set the heater to max heat before doing the test.

If you can't see any leaks, replace the radiator cap and check for a blown head gasket.

Bad raditor cap blown head gasket bad over flow tank

Head gasket. Get a compression test

If you have to add coolant/antifreeze often enough to notice, you STILL have a serious leak somewhere. More than likely, you replaced a perfectly good radiator for no reason.
Now it is time to have an actual mechanic find the REAL problem.

Only half the coolant is in the radiator, the rest is in the engine block. I think you may not have filled the system properly the first time. The whole system should be about 4 gallons.