03 Protege5 will not reach normal operating temp

Hey guys, so I'm having a few issues with this car. I bought it a few months ago and it has 260,000 miles. it runs like a champ except for a few issues. the car has never gotten up to "normal operating temperature," and now the A/C isn't working. It is strange because it worked this last Friday before I replaced the passenger side engine mount. After I replaced the mount, it stopped working. I just replaced the thermostat last night, hoping the old one would be stuck open, but after my ride to work this morning, it still won't reach operating temp. There is white smoke coming from the exhaust, a decent sized cloud but only when the vehicle is started for about 3 seconds then it stops which leads me to believe, head gasket. But would this play in to this other issue? I'm not sure. any info would be appreciated.
 
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