Can anyone figure out this mystery?

It's possible that your guage may be broken.

jdeter34, Thanks for the input. I've been fighting this car on and off for three weeks and today I succumbed to professional help. I hope what I discovered will help other people with this problem. It was actually the water pump. It wasn't leaking or making a loud noise. In fact, I had it replaced just about 3 or 4 years ago. As I stated earlier, up until this problem occurred, the coolant was "sinfully" dirty. I had not done my job of maintaining the cooling system by keeping it clean. The water pump impellers had completely corroded away. There's was only one left intact inside the water pump. My auto repair guy showed me and I couldn't believe it. I've never had this happen. This explains the temp decrease when I revved up the engine. It was barely circulating coolant. Did I mention that the heater was also not working at all? It's because the coolant was not circulating through the heater core either. It's around a $500 job because it's pretty involved and I also asked them to replace the timing belt because when you remove the water pump it's right there and there's no sense in having to do that repair later. I hope this info helps others because this has driven me crazy. I could not figure it out. Thank you again for the input.

I changed thermostat, water pump, hoses and i still get antifreeze backed into reservoir tank..what can i do??

check your fans one of your friends is supposed to cut on when they're car is about to overheat this fan is not working correctly