Keep loosing coolet no leaksfound - 2003 Chevrolet Suburban

You only have a few options here:

Coolant either leaks out, evaporates, or is exhausted through the engine. Check your oil & see if you notice any coolant mixed in, indicating internal seal issues. Also, you can have a small amount of coolant drawn into the engine cylinder & exhausted as steam or vapor and never notice. If only a small amount and no noticeable engine problems, evaporation. Engine miss sometimes & refilling anti-freeze often is an internal leak, generally the Head Gasket. Very rarely, a transmission (automatic only) has been found with antifreeze in it due to a leak in the radiator/transmission cooling system. Good Luck.