One more thought: Do you know how to check your fabric to make sure you have it on straight of grain? That is, fold the two ends together and putting the to selvedge edges together and allow the fabric to fall free from the edges. Are there any wrinkles showing in the fabric? If so, move one side of the fabric to the left or the right til the wrinkles disappear.
This means that the fabric is now folded on the straight of grain.