What is wrong with my car?!?

I have a 2003 Dodge Intrepid SE 2.7L. My RPM will not go over about 2500, my gas mileage is horrible, and it feels kind of jerky sometimes. I got an error code that said the camshaft position sensor is bad so I changed it and its still doing the same thing. I put it new catalytic converters , got a computer reset, new oxygen sensors and nothing helps. I googled alot of things and nothing seems to help. If anyone can help me I would appreciate it cause I'm so tired of spending so much money and time for nothing lol