2006 Chevy Cobalt white smoke

I drive a 06 cobalt. Lately the check engine light has been going on and off. Not blinking, but when it rains, it will always go on. Then about 3 days later after I drive it here and there, stop here and there it goes off. Whenever I start my car I hear this swooshing sound behind the glove box. There is no antifreeze on the floor and none on the ground. Somehow there is antifreeze that is "disappearing". I had it to a mechanic 3 times for this, and they plug it in and they say everything is fine and there are no leaks. I keep up with the oil changing it every 3000 miles. They did a coolant flush and that lead to it overheating about 2 weeks later. Turns out they didn't put the car on an angle while refilling it and an air bubble worked itself out, or so they say. The thing is lately the check engine light has stayed on, no rain mind you, and I notice this white cloud of sweet smelling stuff come out. I know this is antifreeze, but it just started doing that. As always adding antifreeze. My car has been running around 220-240 on average and the fan is running. It is hot outside, but I am not in stop and go traffic. As I said before the check engine light isn't blinking. Help!