Carey,
Folding a fitted sheet is not too hard. It won't look perfect but here is what I do: Keep in mind, I am not the best at describing things.
Take two of the four corners and intermingle them, like over your fist, then take the other two corners and do the same, so, they are matched like the other end. Then you take those two and place them together, folding the fitted corners "into" the first two you folded.
Then, I lay it flat (as possible), the fitted corners should be all kinda cupped together, fold the edges of the sides in towards the middle, you will have 2 of these sides.
Now, it should look like one of those little baby blankets or baby towel with the little hoodie attached on one corner but the rest is flat. Relatively square.
Continue to fold in half until you get the size you desire. It works pretty well, for me anyway!