1995 Chevy Monte Carlo problems with over heating

1995 Chevy Monte Carlo Automatic

before starting my car this morning, I checked the fluids, refilled the coolant and such, everything seemed fine. But by the time I had traveled a mile, my car had started overheating. I turned the heat (which was ice cold) on full blast, and it continued to overheat, so I pulled over. After it cooled down, I checked the fluids again, they were fine, so I tried to go home, but about another 2 miles and it began to overheat again. Around this time my heat kicked on and the gauge went about an 8th of the way down. Suddenly my heat went ice cold again, but the needle remained where it was. A few moments later, the heat kicked back on and the gauge went the majority of the way down, but, again, the heat went to ice cold and within a second or two, the gauge shot back up.

our heat has been doing the cutting in and out, but this is the first time we've had any problems with it over heating.

any advice?

anyone?