strange problem

I just recently purchased a 1998 bmw m3 I love the car my favorite ever anyway I was driving it this morning and itdid something that I've never had a car do before I was excellerating heavily atd a slow speed under 40 miles an hour when all the sudden the car started reving up as though it wasn't engaged in gear I let off the gaslook down in the car was still in drive so I put into neutral coasted for a minute thento put it back in drive in the car rev really high I guess I braked and the car finally shifted but then the engine ran extremely rough for the last half mile home set still with it idling and look at the engine and looked underneath the car didn't see anything abnormal butt it continued to idol very roughand the check engine light came on and it was making a repetitive squeaking noise from somewhere underneathI cut the car off restarted it and its idling fineand the c:heck engine light is still on any ideas guys I even drove it a few 100 yards up to a gas station in it seem to drive fine not running hot oil looks fine

That's the longest sentence I have ever seen. Anyways... I'm assuming this is an automatic transmission?

Yep...the car is running fine now. Im assuming the rough engine was some kind of governor that engaged. I was turning hard right before...could the transmission fluid have gone to one side and it missed a gear? I guess I'll have to cough up the 80 dollars to run a diagnostic to get the check engine light to go offand probably find out what happened. does the transmission fluid ever run low? am I able to add anything to it?