Since you are tracking your progress, compose your photos in a way that captures your whole treatment area. You can get great shots by placing yourself in the center of the photo frame, but there are many other options, too.
Try using the rule of thirds. Imagine your image has two vertical lines and two horizontal lines running across it. Frame yourself at one of the intersections, and let the background fill the rest of the frame. This adds negative space to make for a more interesting composition.
Also be sure to consider your background. Nothing ruins a photo faster than a cluttered, messy background. You want people to notice you and your progress — not the piles of laundry on your floor. (Just us?)