Having trouble changing sprites in 2 dimensional animation

I am trying to create an animation which will change the sprite every so often, the way i am doing this is by adding a sprite curve under the sprite renderer in my animation. It looks like this:
23960-kpvypwd.jpg
Now this doesn’t seem to work, and acts quite strangely. First off immediately after doing this and then previewing it in tha animation it will only use the sprite that has most recently been set, regardless of the timeline.
Secondly it will revert the sprite to the normal image whenever I play the scene, save the scene, or select another gameobject among an array of other weird actions. As a result the sprite always seems to revert.
It seems like I am doing this completely wrong, so can someone please help me.
This is a 2d project.

Are you using an AnimatorController anywhere? Usually you would use an Animator on your character and have it reference an AnimatorController which would control the animations you make. Other than that, I can’t tell what the problem could be, but I’d suggest looking at http://learnunity2d.com/2d-character-controllers-tutorial/ for some help setting up 2D animated characters.