Should I BD tonight? (faint line OPK)

I think I've answered my own question:

Q: What does it mean if my test line gets darker for a day or more before the actual positive?

A: Some women have a fade-in pattern where the test will get darker for a day or two before the positive result. This generally isn't anything to worry about, and may have the benefit of a bit of advanced noticed. If you find you have a fade-in pattern, you should begin having intercourse when the fade-in pattern starts.

I would do another test tonight, and then BD if it's dark.

I did a second test last night and had a very very faint second line so left it till today. Thanks for the advice guys.

It's always hard to know what to do the first time you use OPKs because everyone has different results.

My experience however is that I could probably get a faint line whenever I tested. I could be several days away from ovulation and still get a faint line. About a day before the luteinising surge it would start to get darker on me until I got a nice dark positive.

So if it was me I wouldn't BD on a faint line. Like someone else said, I'd test again tonight. Also, you tend to have 12-36 hours from positive OPK before you ovulate. I suspect the 12 hour thing would only happen if you weren't testing frequently and so 12-23 hours had gone by since the surge. (I usually tested 2-3 times a day when I suspected the surge was about to happen so it was pretty much always 36 hours for me).

The cycle I got pregnant this time around, I got my positive OPK in the morning and then we BD'd only once that evening. I would have ovulated sometime within the next 24 hours.