ThisTime I agree with 1000 that if all your symptoms Point to ov, that's really really likely to be it. I've found the apps to be out the last two months, and my symptoms correlated with opk results. What date did your last AF start?
Don't be scared of symptom spotting here iamchanging, we've all embraced the madness! On a serious note symptom spotting, along with bbt and OPK has really helped me u derstand the my recognise the stages of my cycles, and TTC aside, it's been really interesting and beneficial to my everyday life.
Oh pocket, I really feel for you, we've all been frustrated by our 2ww! I really hoping your colour change isn't AF. Let us know!
Having said that, I've been caught out being over confident. I usually chart and OPK from really early but as Opk's and symptoms and been definite for LH surge on cd16 on the last 2 cycles, I started on the 12th (ish) and didn't record them, or take photos of my Opk's. The firest 2 or 3 days has really faint lines and I didn't think much of it as I was so confident about Oving on cd17. But it's now cd18 and they're snowy white. Whigh means I'm either Oving later, missed it on the sticks (poss caught tail end???), or maybe not going to ov at all. I can't be sure because I was so slack! So annoyed with myself. At my afe (40), I can't afford to waste months.
Also, (TMI alert) I had smelly pink tinged discharge on cd11, 2 days after BD. I washed with saline solution and it cleared up so I'm putting it diwn to a Bout of mild vaginitis...but could that have been ov spotting? 
sorry!