Hi Monika.
with the OPK's not so much the lines you need to worry about it's the colour of the lines, you can have LH in your body all the time and the test can pick it up, but when your going to Ovulate the LH gets really strong making two lines of the same colour (very strong pink/red) the test line needs to be the same colour or stronger than the control line, if so then you have a positive OPK, if you have red Control line and Pink Test line thats a neg,

I usally start to get the 2 lines one red one pink (neg) on day 11 and 12 followed by a 2 red ones on day 13 Positive so I know when it's going to come, it usually last positive with me for 48 hours then I go back to one red one pink (neg) for a day or so, then back to one line.

hope this makes sense
Bella
xxx