Just a quick question...
What does it mean if you are wearing a somewhat fitted top and the back folds ups in a couple of spots instead of laying flat against your back? Does it mean the top is too small or too large?

Are you talking about folds of fabric that appear above your waist or near your shoulder blades? If so, for me that usually means the shirt is cut too long. Many women's shirts have a smaller waist already sewn in. If the waist of the shirt is lower than your natural waist, then the shirt shimmies it's way up so it's waist sits at your waist. This usually results in extra fabric at the back, even if the shirt looks okay from the front.

If this isn't the issue you're having, maybe post a photo?