Is anyone using these? I'm getting so frustrated, as my cycles have quite a big variation. I tend to alternate between long and short months, with a short month around 26 days and long up to 32 or 33. I'm on CD 13 right now and so have been using the opk for about 5 days and NOTHING. It's not getting even a little darker. Is that normal? It seems like it should get darker as it gets closer, but I guess I'm not even getting close? I guess I'm just concerned that there's ZERO change so far, even though I am hopefully getting close!