What is causing my 2004 ford explorer to overheat I changed the thermastat and didn't have a problem with it for like 3 weeks now it got so hot that the engine cut off and there was no fluids left in the tank

Blown head gasket, due to overheating an aluminum head engine? Check for coolant in the oil.

It may be overheating due to phosphate scale blocking passages in the radiator. Replace the radiator and refill with a 50/50 mixture of G-05 HOAT antifreeze and distilled water.