I don't have white smoke at cold starts at all, but I smell some sweet odor for the first 30 seconds. I'm not sure if there is oil in coolant.
I have to add about 4oz every two weeks in the reservoir. No overheating, but once, because of the bad thermometer, which was replaced right away.
Do I have early symptoms of a blown head gasket?

 

Maybe? Read this http://voices.yahoo.com/automotive-t...et-504515.html and this http://www.ehow.com/about_5443821_sy...ad-gasket.html and afterwards check your car and report back. A compression test of the cylinders would help too. You can get a free loan compression gauge at advance if you do not have one.