I completely and totally agree with Kara about Spanx (specifically the Hide and Sleek High Rise Panty ;) if you're interested!). It will tighten and smooth your midsection by a couple inches, but if wider hips are the problem, it may not help so much. There are probably other slimmers that they make that would work for that, though. It took about nine months after delivery for my hips to return to their normal state. The positive, of course, is that they did return - almost overnight, it seemed (nine months later, but very rapidly after that).
You could just buy some knitwear. I think JJill sells a lot of the flowy, stretchy knits that look professional (you're in a school, right? It was dress appropriate when I was teaching). You could by a couple pieces to get you through, and still be able to wear them after you get back to your normal shape. How soon 'til you go back?