2002 Ford Focus zx3 still overheating?

[Rachelle]

i got this car in march and i have already spent 1000 dollars in work on it first, the alternator went out so i got that replaced, then the car started overheating a little when driving on the highway but the temp would go down when you slowed down so i got the thermostat replaced and the mechanic told me that i still had a clogged radiator and it will need to be fixed soon so 2 days ago i did get a new radiator put in but on my way home the temp gauge went all the way into the red the farthest it had ever went but i didnt see any smoke or anything but i did stop every 3 miles on the side of the road to make sure that i didnt break anything and i got home safely. i called another mechanic he said it might be the water pump, a cracked head gasket but i checked the oil and it wasnt milky, or a water bubble in the radiator, i just dont knw what to do could the temp gauge be broken??? thanks for your help