I am new to knitting and taught myself. I am working on a scarf. The pattern calls for knitting one row then on the next to knit 6, purl 6, knit 6, purl 6, knit 6. My purled sections are puffing out and the knit rows curl under. What do I need to do to get it to stay flat? If I lay it out it will lay flat but as soon as I pick it up it curls back up. Am I switching from stitch to stitch wrong or is it a tension issue? Any help you can give would be wonderful!