Help!!

I was driving to my gf house yesterday..half way there..i heard this quiet sound like something just fell of my car(not sure)..once i got to my gf house..the whole engine started to shake when i put the car in Park..i was like what the heck?..soo..i open up the hood..nothing seem to be wrong..so I took the car for a test drive..and boy..it was shaking and lagging everytime I rev..then..i put my car in Neutral..Rev my car..and behold..the engine went back to normal..wasn't shaking or laggin anymore..and then the Engine Check Light went on..and that was that..Anyone know what just happen here? Please help me out..any info would help..My car drives normal now..but I fear something is wrong..I might need to go to the shop for this..so give me some ideas. Thanks guys.