How, exactly, do you not have enough sts?
1st row: 6sts
2nd row: knit
3rd row: 6sts + 2 yo's = 8sts
4th row: knit
5th row: 8sts + 2 yo's = 10sts
6th row: knit
7th row: 10sts + 4 yo's - 2 ktog = 12
To break down row 7: k2, yo, k1, yo, k2tog, k2tog, yo, k1, yo, k2
Actual sts needed, without counting yo's: k2(2sts), k1(1st), k2tog(2sts), k2tog(2sts), k1(1st), k2(2sts) = 10sts.
Your k2tog bring the count down to 8, but your 4 yo's bring the count up 12.