Hi, I'm not an expert. I've used them too before, but it won't show any more positive or more negative because of sex. If you know more or less when you think you ovulate (I usually go according to the cervical mucous, because I forget to temp) you start testing. You will probably start of with neg results (only one line or or the result line is much lighter than the test line). Once you get your LH surge you will see the result line will get darker than usual. A positive result usually is when the result line is the same darkness or darker than the test line. I have read about women who never get a real positive when they use these things, but that their result line does get a bit darker. Not everyone ovulate every month, or at the same time of the cycle. I usually ovulate 14/15 days before I get my period. How long is your period usually?

Thanks..
My cycle is every 26-28 days. I just see the OPK come up slightly fading after the surge. Is it like this the 2nd line supposed to be completely gone?right fatre your surge

I think these things work differently for some women. When I used it, for the first one or two days there's a faint second line and then usually by the third or fourth day the second line will be darker than the test line, which is my surge. Maybe you ovulate earlier than you think? Do you temp or check your cervical mucous? I forget to temp, but I usually get 'egg-white' cervical mucous from about cd14 to about cd 17. Then I know the surge is close. Have you noticed that the result line maybe get darker than it usually does, even though it's not as dark or darker than the test line? I've read that that can also indicate a surge.

Good luck.