Car Trouble. '02 Ford Focus?

The last time I drove my car was maybe 5 or 6 days ago. Today I turned it on and white smoke was coming out of the exhaust and the car started to shake (more than normal; i know it's an old car) almost like from front to back?! It was absolutely fine the last time I drove it and I haven't noticed any leaks (unless it dried up before I saw it). Any idea what this could be? (i'm a poor college student who knows nothing about cars!)

Added (1). *No check engine lights or any other lights are on*

It could be condensation build up in exhaust system. But it could be head gasget… Take it for a run.see if its still misfiring… And white smoke… White smoke can only be water. You may have a misfiring spark plug. But I can't see the car from here!

White smoke is head gasket…