I've been on vacation the past week and when I know I'm going to be Oing when I'm away, I take a few OPK's with me in my toiletries bag. I took one Friday and it was not +, but the test line was there. I took one Saturday and there was almost no test line at all. And I took one this morning and it was definitely +. Usualy, the test line steadily gets darker as I approach O so it was odd to have a line, then none, then a full +. I think it's possible that I might have grabbed an old OPK from last month that I'd accidently left in the bag (I was away at O time then too) so maybe with all that air exposure it went bad.
It's not a huge deal, but I'm really hoping I O'd yesterday (I'm not "scheduled" to O until Monday or Tuesday). We BD'd Wednesday, Friday, and twice yesterday (happy 4th! lol

) but with BF going back to work tomorrow after a week's vacation, I don't think he's going to be up for any more BDing this week. My temp did drop down to 97.2 for 3 days then mini-jumped up to 97.6 today so hopefully my temp will keep going up and show that I did O yesterday (despite the almost not-there test line on the OPK).
Anyway, guess I'll have to wait and see what tomorrow's temp does.