Q: Shaking and poor fuel mileage

Hi there, I'm not in your country but would love some advise as we don't have this sort of reliable service in New Zealand, Auckland. I have a Nissan Primera 2005. My car shakes when in idle, drive, reverse you name it! Getting to the point where gas is being burned like nothing after just fuelling up. Not just a little shake either this shake rattles the entire car as if I was in an earthquake! Non stop shaking and it's even worst when I'm driving and I can now feel it when I slow down to brake the car jumps forward. Changed spark plugs, changed enegiene mount but the problem is getting worst. When I start the car shaking happens and the engienes always loud. When I change to drive (it's an auto) and accelerate the is still idle and shakes even more and then jumps and bunny hops before picking up speed. The shaking is constant throughout the car and is always shaking unless off. You can feel when changing gears! Need advise please as I don't have money to go to a rip off place! Help!

My car has 197756 miles.
My car has an automatic transmission.