Overheating?

I have a 95 ford taurus that I have to fill the radiator often...like every couple of days. I have looked for leakage under the car and do not see any. Fan works fine, there is no coolant in the oil, no white smoke, I bought a new radiator cap. Next step is the thermostat. yesterday with the old radiator cap, the radiator cap was cold when i overheated. Today I did not overheat but the radiator cap felt warm. Seems that the coolant is disappearing while driving. Can this leak out only when driving? Also when I walk around to the front after engine has been running...It smells hot, I can smell the coolant.Any suggestions?