Why engine overheat and the fluid is gone fast.

If the coolant is disappearing fast, lost of power, white smoke from exhaust,and no visible signs of a leak then one would have to conclude a broken head-gasket or cracked block or head but I would rather think it is a head-gasket myself for now.A pressure test on the cooling system would confirm.I also believe that if there is a blockkage like a collapsed radiator hose or blockkage in the radiator it could make the water boil away but I suppose one would see the steam.

IS THERE ANY EXTERNAL COOLING LEAKS?