So we've been trying to TTC and I started using the OPK test strips from amazon. All have been negative so I dropped the $40 to get a clear blue kit. I was so excited and hopeful and it's a big fat negative O. I'm on CD 15 and am at the "end" of my fertile window... is there any hope for me?? I know it's not a negative pregnancy test but I'm still heart broken. My body can't even do what it's supposed to do...