I am making Kate's Cap by Design by Louise. I just knitted 6rows on circ needles, then switched colors and did K1, slip 1 for a round. I am about to start a purl row. But when I start the new round with purling, I end up with an extra loop on the needle. I have ripped it out twice to try to fix it and don't know what to do... Any way to fix this? What am I doing wrong?