03 lancer es wont shift

Hey fellas, I have an 03 lancer that was jerking when it shifted. I flushed the transmission fluid out and replaced but now it wont shift, it stays in one gear and thats it. Ill go 70pmh and my RPM's are at 5000-6000. When I put it in reverse it jerks pretty frikkin hard. Does anybody know if I just need to change the Transmission filter out, I pulled the codes and it said something about my O2 sensor. and said something about my gear 4 ratio. I need some help please.