you're purling your way back on the WS.
it sounds like what you need to do is find a stitch 6 rows down, put that on your needle and then p2tog. and repeat this the whole way across the row. for every stitch, you're going to pick one up 6 rows down, add it to the needle and then p2tog.
it's going to gather the row you're working on with the one 6 rows down and create a fold which is the ridge.