1999 Plymouth Breeze Temperature Gauge

This has happened to me 3 times already. First time, I was driving on the highway and I went to the mall, and I noticed that the gauge was at the red line. So I pulled over, blasted the heat inside, and tried to get it down but couldnt so I towed my car home. I brought it to the mechanic and they fixed it. 2nd time, I noticed that the gauge was starting to go up again, and there was coolant that leaked. So I had it fixed AGAIN. For a while everythings been fine, but now its starting to fluctuate now. And my heater doesnt work until the gauge goes up real high, and when it goes back down, THATS when the heat starts working. I checked if I had antifreeze, and I had to pour more in. I checked if there were any leaks or if the hoses burst, but everything was fine. So I just thought I needed more coolant. For 2 weeks everythings been ok, I got used to the fluctuation. But today I drove and then the gauge actually got up to the line rite before the red one. And when I got out of the car, it smelled like burnt rubber. Why is this ALWAYS happening?