Hi there and welcome to the Owner's Forum.
First thing you need to do is get it plugged into a diagnostic unit and get the error codes read. Once you have those, it will give you an indication of where to start looking to fix the problem.
By what you say, it sounds as though you have gone into that well known area of the "Limp Home Mode" - You have very slow acceleration, increased fuel consumption and the engine won't rev over 3000 rpm... What is happening is that the ECU has sensed that there is a problem somewhere and runs the engine on a fixed programme of lower revs and richer fuel settings, designed simply to get you home, without damaging the engine.
You will probably find the problem is in the Air Inlet Manifold or with the EGR, if you have one fitted.
Good Luck and Cheers... Robin