Engine overheating?

My car runs great with the air on while I am in constant driving without very many stops. When I stop a lot or constantly it starts overheating. I turn off air conditioner and the gauge goes down real fast. It has coolant but a little more then it should.

Hi, I was wondering if anyone could help me? I have the van listed above it has been losing radiator fluid somewhere (not in my driveway). Been just refilling it all the time. Well today while driving my van just shut off. I do not know if it overheated as I did not notice until it shut off. I suspect it did. I pulled off and tried to restart it and it kind of tried and then started clicking. I was able to let it cool down and then put antifreeze in it. It had none. Still would not start. Then I got a jump and it started and seems to run fine. Took to advanced auto and they said battery, alternator, and starter are fine. Does anyone know if I may have done damage to motor or if this van has something that senses danger and turns off on its own to prevent motor problems? Any help would be appreciated as I am clueless to this stuff. Oh and I do not have antifreeze in my oil. Not sure if posting in right place. Sorry if not. Â Â