Acceleration problem

Is the check engine light (or any other) on? It sounds like it could be in "limp mode" which can be caused by many things. The first thing to do would be to use a scan tool to see if it is in limp mode. If it is then there are a lot of items that could cause that.
If you step on the gas with the transmission in park does the engine rev freely? What did the car do just before this? When it is in gear and you step on the gas does the engine rev up but the car not move? If that is the issue or if the engine revs up and it slowly speeds up you have a worn clutch that is slipping.