Sorry but it sounds like the slush box is dieing. It is a common weak point on automatics. The 4hp22 (the tranny) A pack has died. There is a good write up on how to fix it on Mye28.com. You can either replace the A-pack, get another rebuilt or used tranny, or do a manual swap. If you get a used tranny you might have the same problem in a year, A rebuilt one will cost a lot. Getting a manual swap will cost about 500 dollars. It is rather straight forward on this car to do.