Are you doing the k2tog part? If so you should have the same number of stitches. It sounds like you're adding extra stitches somewhere.
Written out round three would look like this:
k2tog, k2tog, yo, k1, yo, k1, yo, k1, yo, k1, k2tog, k2tog, repeat...
Those 4 - k2togs decrease the 4 - yo,k1's back to the original number of stitches.