Wheel Related Problems of the 2008 Mitsubishi Eclipse

Wheel problem

I brought the vehicle used in 2008, after driving for a week or 2 I notice the tires were loosing air. I am constantly filling the tires with air every 2 to 3 days. I have taken this vehicle to the dealer and 2 other shops for a diagnosis and they said it was the tires, I replaced the tires and I still have this issue, so I know its more than the tires (its probably the wheel element damaged or something). The light tire lights turns on constantly and on several instances the car would shake heavily. Most of the shaking is experienced when driving on the highway. This issue is so bad, I barely ride the vehicle and when I do, I do not take it far due to the air pressure issue.