94' Jetta Auto Shifting Problems!?

I drive a 94' Jetta GL auto transmission and sometimes it has issues shifting. Occasionally my car will get stuck in 2nd gear and the rpms go up and up, but most often it gets stuck in 3rd gear and will be going over 4000 rpms at 100kmh. If i press the gas to the floor and let go quickly sometimes it will shift and drop down. Anyways it is gettng frustrating, even though i have more acceleration power i don't want to be driving on the highway at such high rpm's... any suggestions?!