I had a scan at hospital on Monday and the nurse said it looked like I would ovulate within the next 24 hours.

I've been doing opks twice daily since and not had a positive opk.

Im now on cd 18 and this afternoon I did an opk but then forgot about it for over an hour and when I looked at it it looked positive?! Could this just be because I left it for so long?

I've just done another opk and it isn't positive.

I'm so confused as nurse said it would be within 24 hours when she did my scan on Monday and now this opk looks positive to me but don't know if it's just because I left it over an hour?!

I typically ovulate between cd 14 and 16

First pic is the one I left for over an hour and looks positive

Second pic is one I've just done