1999 Saturn SC2 DOES ANYONE know?

I noticed on my way from indianapolis to evansville my car wasnt running right. I had three hours to study its behavior and this is what it was doing. I would be going a steady speed of 70 mph and my car would slowly but steadily drop down to 60 mph without me releasing any pressure from the gas pedal. In order to get it back to 70 I would push the gas pedal harder and then the engine would rev up and the rpm gauge would stick at 4 until I let off or hit the brake. I also noticed when I would use cruise control it would rev up again the same way; maybe to maintain the speed? My step dad says the throttle body needs cleaned and my father says its my transmission :(