Thats why you always buy more than you need for your project. If you cut it so close that you worry about a few inches of fabric you'll be disappointed every time. I learned a long time ago to buy at the very least a 1/2 to a full yard more than I needed because when I didn't I regretted it. The up side to that is...I have a very cool stash. =)
When you cut you never line up the selvages but the fold. You slide the selvages until the fold is straight and then even your edges. Sometimes the selvages are way off sometimes their not. It happens with LQS fabric as much as with the bargain fabrics.