Dude, if you want the easy way, think about it like this:
1---2---3---4
The whole sprite is this long
<----------------->
and you check collisions using collision points. Why do you need to really move it around?
Make a variable positionNum and subtract 1 when you press left and add 1 when you press right (since it doesnt get <1 and neither >4) and player.setframe = positionNum
If positionNum =1 it will look like this
<------------------> (this is the width of your sprite, with blank space, just use collision points to make it collidable where you want, each frame) and I think your problem is solved with 3 or 4 lines of code.