2002 Chevy Impala, Car issue plz help?

In the last 2 years I have gotten replaced small things like brakes, wheelbarings, Muffler, Fuel Pump, altinator, Spark Plugs. We had only replaced on Tire on the passenger side since we had it. The motor seems to be doing okay... But for about 3-4 months we have noticed a Vibration coming from somewhere under the car? Wobbles, Bumps... Hard to explain! The faster you go is the worse it gets. It sounds and feels horrible! Today we went on a 100 mile trip and it had gotten louder so we are wondering whats causing this? When your driving the Car it Pulls to the Left some, Its driveable But very veryyyy annoying and afraid it could be something serious? The motor seems to be doing good its just like its coming from Underneath, Maybe even in the front end? Any ideas?? Answers GREATLY appreciated! And 10 Pts will be given for the best answer.. Thankyou for your time!