2005 Pontiac Sunfire FEELS LIKE IM DRIVING ON FLAT

what would you consider driving on a flat. please be as descriptive of your problem as you can be.

WELL I WAS DRIVING HOME FROM WORK AND WHEN I STARTED OFF I FELT THIS FEELING LIKE MY CAR HAD A FLAT GOT OUT AND LOOKED AT ALL 4 TIRES AND I DID NOT WHEN I STARTED TO DRIVE IT FELT LIKE I WAS DRIVING ON A FLAT THE CAR HAD A ROCK TO IT LIKE I WAS DRIVING ON A FLAT
AS I PICKED UP SPEED GOT WORSE THEN IT GOT A LITTLE BETTER AND THEN CAME BACK AGAIN WERD RIGHT ...

I WOKE UP TODAY TO A FLAT ON DRIVER SIDE REAR TIRE ..BUT IT FELT LIKE IT WAS IN THE FRONT .....FRONT WHEEL DRIVE SHOULD I HAVE FELT IT IN THE FRONT IF THERE WAS SOME THING WRONG WITH MY TIRE

if you have a tire in the rear you would most certainly feel it in the front. could even cause the car to swerve so bad it be undriveable!