Oh, no!! Wrinkly stitches!! Are you pulling out a few inches of the threads, top and bobbin, and holding them down behind the needle before you start a seam? This keeps the thread from bunching up at the beginning of the seam as you start stitching. Another way is to take a scrap of fabric and start out on it, about a half inch of sewing on the scrap, then slide the good stuff on under the needle. I do this at the beginning and ending of my seams, then clip off my scraps and go again with the next set. If its not that you could be having problems with the needle size not paired to the thread size, or putting the bobbin in wrong side up/out which means the thread is feeding off the bobbin the wrong direction. Worst case buy some more upholstery thread. I know, a trip to Wally World, look for the spools near the bottom of the Coats and Clarks thread display case.