UPDATE: ok - went to the orthopedist. Because my MRI came back clean and the Dr didn't feel a mass, he was convinced it was because the anticoagulants I injected while pregnant killed the fat cells, and leaning against my desk caused the horizontal indentation.
He said this thing hapens because a) what I just explained (fyi - steriod injections are also notoious for doing this) or b) there is a mass or tomor that causes the surrounding tissue or fat to be raised which causes the appearance of an indentation.
I encourage you all to see a Dr to rule out the later. He also said that prior trauma to the area will cause indentation if pressure is applied to the area (such as leaning against a desk). I found out today that my dad has something similar from slipping while on a ladder and hitting his thigh on the metal edge of the step.
oh - the dr aslo said there is nothing you can do to repair it except losing weight so that it isn't as noticeable.