oil burning, heat blowing cold when I dont give the car gas

Hello, this is my first post here. In the last few months my monte seems to be falling apart on me. My main concerns right now is that it is burning oil, I get regular changes and they swear up and down that it is not leaking oil so it has to be burning it. Also my car will give me heat when i am pressing the gas but as soon as i let off or stop at a light it blows cold, it blows fine the temp it just messed up. I was wondering if this could be a thermostat problem all around? It seems when my car is warming up the temp guage gets to the half or more then as I begin to drive it the temp falls quickly like the car is cold, I dont get it, If I am idling at a light my temp gauge also goes up past the half like it is getting to hot. PLEASE HELP ME..... It is getting very cold in chicago..


My Monte is a 2003 LS 3.4

It is normal to use some oil between oil changes. How much are you using? Do you see any blue smoke coming from the exhaust? That would indicate burning oil.

As for the heat not working unless you give it gas, it could be a water pump issue.

I have not noticed any blue smoke from my exhaust, however sometimes I can smell the oil burning, usually after I exit the car. When my oil light comes on I am already 2 quarts of oil low and I am not sure how healthy that can be for my car to run that low. Also I want to think that the oil and heat problem are related some how because it all started happening at the sametime. Could this be a thermostat issue? If it is not working properly maybe my engine is running hot and burning oil, also if reading the temp wrong that can maybe explain why my heat does not always blow hot. This is all theory and a guess but I would love if someone could give me something, point me in the right direction or one that could help me out.

Thanks

Could be a blown head gasket.

Remove the oil cap and look at the bottom of it. Does it look milky?