2004 Transmission Bucks between gears

For the past 3 weeks, my transmission bucks right before it shifts and is getting worse day by day. I had a tune up less than 2500 miles ago. I checked the transmission fluid and it looks fine. The check engine light came on 2 weeks ago and I changed gas stations as the manual suggested in case it was that and the light did go away. Before I bring it to be looked at, any suggestions?

Look at the transmission fluid again. If it has bubbles, you have a pressure valve problem. If it smells burnt and like metal, then you're grinding gears. If it's discoloured, you may have contamination. I would take it in asap if you value your transmission.

Sorry, I forgot to tell you to check your transmission fluid WHILE THE CAR IS RUNNING. Drive it around for 5 minutes in all gears, including reverse. Then park it on a level surface and keep the car running while it's in park. Then check your trans fluid.