Cheap opks. Can't understand them

[BlueWater]

So atm I've only been using cheap opk to predict ovulation. This month is month 2.

I usually average a cycle of 27 days.

Month 1 I got a positive CD 13 and had a 12 day luteal phase resulting in a 26 day cycle.
Month 2 I've got a positive CD 11 which means FF has predicted this cycle to be a 24 day cycle.

Is this common, or am i reading my cheap opks wrong?

 

[xCookieDoughx]

You may be reading them wrong as I was sure I was getting positives as the line was almost identiacally dark to the control line but they weren’t. It wasn’t until I got an actual positive today that I realised. The test line has to be darker than control.
This isn’t a very good pic but hopefully you can make it out xx

 

[happycupcake]

If the test line is as dark or darker than the control line then it's positive. It isn't uncommon for the timing of ovulation to vary, I wouldn't worry about it. I ovulate anywhere between CD9 earliest so far and CD14 longest so far. Usually ovulate CD11 or CD12 on average and my lp is extended because I'm on Cyclogest

 

[Dill]

As always, cupcake knows her stuff!

 

[happycupcake]

Dill

You know I didn't remember to say that it is quite normal for cycles to vary in length. Luteal phase generally stays the same, doesn't usually vary by more than a day or two if any, but the day you ovulate can vary which is why cycle length can then vary.
OP do you temp? Only real way to know you definitely ovulated, OPKs only tell you you may be about to ovulate