Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
The first thing that you want to do is check the cooling system for any exhaust gases. There is a tester for that, that you can gt from Autozone for about $20.
Block tester available as:
Napa BK.(NNN) NNN-NNNN/p>
If there are any exhaust gases in the cooling system, that will cause more pressure than desired and will probably allow the engine to burn coolant.
If there are, then there would be an internal engine problem, like a head gasket or head. Of course, you will want to make sure that the system is full and the cooling fan(s) are working as well as the pressure cap holding pressure. Thanks