This is my first month using OPKs, cycle 2 of TTC. I am on CD15 and still a very faint line on my OPK. Is it supposed to get darker as I get closer to a positive? Or can it be super light every day and then all of sudden be a full on positive? I haven't charted ever before so I don't know what is normal for me, but I would have thought based on my typical cycle length (28-30 days) that I would have gotten a positve by today or at least closer to a positive.

I am also wondering if how I have been using the OPKs make a difference? I don't usually wait 4 hours from the last time I peed, it has been more like 3 hours and I test around 3:30-4pm.

any advice or tips on what's normal would be much appreciated!