think im loosing coolant...or not?

I added some ccolant to the overflow about a month ago....then i noticed my temp gauge was climbing above half while idling. So i check the overflow and it was empty, and the coolant was down in the rad itself. I just filled up the rad and filled up the resevoir. But it was down again the next day. Now the rad is full and the resevoir is topped up and it went down yet again. Common sence kicked in and i remember for the past month or so the swishing bubbly sound when starting the car up in the morning....obviously air in the coolant lines. Im guessing the lower coolant levels are from the air purging out? I never opened the air bleeder valve. The oil is also clean looking (no contamination) and I cant smell any antifreeze out the exhaust. Is it possible for a headgasket to be leaking (or anything internal) without oil contamination or sweet smell? The tranny fluid is also clean. The antifreeze is not so hot looking....the overflow has a build up of dirty brown crap that looks like its been there for a while....and the guy who had it before me told me it had regular green a/f in it but i found out it has DEX-CRAP in it...and i mixed green in with it. Bad thing or just change the coolant before winter?

Yes it could be do to air purging out of the system.

Which engine do you have?

Any white smoke coming out of the exhaust? or a sweet smelling exhaust?

I had the same on my 99 3.8 If you have a 3.8 engine check the plastic elbo at the base of the idler pulley and the intake manifold on the passager side of the engine, that is were they start leaking. 1st fix your leak then do a complete fluid change. Just keep on adding water till you find the leak