if you do decide to prewash be sure to finish off the edges beforehand, or the edges will fray so badly you'll have o fabric left at all. but i would call the 800 # of the website you bought it from, and then the 800 # of the mill
first, in case they're willing to take it back. only after getting no results would i try all the good suggestions here.
P.S. Debbie Mumm fabrics come in different qualities, unfortunately. stores like joann carry the lower quality, for an example. online you can't know which you're getting unless you shop a reliable website. then they should take it back within a reasonable time.