Is there something wrong with the Shrek Forever After storyline?

I noticed something in the storyline.. in Shrek Forever After, it is shown that Shrek was not born and Fiona escaped herself and lived in ogre form. But according to the second movie, prince charming should have saved her, regardless of whether Shrek was born or not. It also shows he was successful in reaching the room on the top of Fiona's tower... so is the story wrong or did i miss something?