Pretty sure I'm out this month :(

Well I've been wondering why I haven't noticed any symptoms this time around and after a neg test at 11 dpo and waking up this morning to see my tempt has dropped I'm pretty sure it's because I'm out this month :( I thought for sure we would get our rainbow baby this month....going to try to start opks earlier this time I'm pretty sure my fertile window is off here in glow....I got a pos opk this time though so I'm confused....anyways where do u buy those plain test strips at for ovulation? I think they refer to them as wondfo?