For the past 3 days my OPK's have looked almost positive but not quite there... and each time I think "tomorrow it will be positive"... and then it's not.
I'm starting to get worried that I won't O this cycle. I know I'm only on CD 13 but I usually have a +OPK by now, and typically O between CD 11-14. (except on post-loss cycles, then it's later)
Has anyone else had this happen and then it finally became positive? Or just had almost positives and not ended up Oing at all?

Re: 3 days of *almost* positive OPK's
My BFP Chart
I feel like I'm in the same boat as you!
I have been using OPKs for 3 months now although I just switched brands. I was using an off brand from the BX (military store) and everytime I tested it was always negative. I'm honestly not sure it if is me or the brand but I tested for like 2.5 weeks straight both times and I'm having issues with my cycle.
I just switched to the First Response OPKs and I swear almost everytime I test it is almost positive. I mark it as negative though since the box says that if it is lighter than the reference line that it is a negative surge. After these are gone, I'm going to try the clear blue easy OPKs since there is no room for wondering if a faint line is a positive or if the faint line will get darker after 12 to 24 hours (since I will be able to see a smiley face vs a circle...no room for interpretation).
But I also know that something is off with me so I may not even be Oing. I have only recently started temping.
TTC Since Aug 2011/
ME:34 all clear/DH:41 DX Severe MFI/
IVF w/ICSI OCT 2012 Stims started 10/8/ER 10/19/12/ET 10/24/Beta#1 11/2=BFN (beta was 1.2)
IVF 2.0-Baseline 11/7/12 beta 0/All Clear
Stim start 11/7/12//ER 11/19 11M//10F
ET 2 embies 11/24//Beta#1 28 Beta #2 23 Beta#3 29
stop meds Beta#4 37/C/P 5W5D EDD:8/12/13/IVF#3 in Jan
Ivf 3-frozen 3 poor 3day/fet=bfn
My Chart//>
I did that this cycle. I tested 2 times a day for about 3 days and all were almost positive, then the line started getting lighter. My temps show that I O'd, though. I guess I just missed it somehow. You may just be O'ing late.
I had similar thing happen last month where I got almost positive OPK's around my normal fertile window. Then never got a positive and it began to decrease in intensity. I had all the standard signs of O (EWCM, cramps etc) but I got very concerned because my temps were all over the place and never showed the standard shift. I kept testing and finally ovulated on day 27 or something like that. The more I thought about it, I realized that I was very stressed at work around days 12-16 and I believe I geared up to ovulate but my stress level got in the way.
Hopefully you will get your positive OPK soon and see a temp shift to confirm it if you are charting.
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This is me too. My temps say that I O, so I just go with that. I don't think I have ever gotten a true positive opk so I always have dotted cross hairs on my chart.
LFAF Summer 2016 Awards:
I usually get positives for a day or two, and it will show up positive at all times during the day (meaning I get + with FMU, SMU, afternoon, evening... doesn't matter when I test) Now I've been testing 3-4X a day and only almost-positives. It's just out of the norm for me.
Tyler (10/29/08)
and Lily (4/21/13)