OPK pic, advice? I think I O'd earlier than normal.

Elaine
Hi ladies, was wondering if anyone could help me, I just a took this OPK and it looks positive to me, I took one yesterday and it was completely negative, I have a 31 day cycle and I normally O on the 21/22nd of every month. Could I have O'd earlier this month? Will this affect my next period? Thanks for your help :)