With cm, although it can be a good sign of ov, everyone is different and won't necessarily see typical ewcm immediately before or on ov day, or any whatsoever. I have the tiniest amount of ewcm a few days before ov and sometimes closer to or on ov day, but usually I see more watery/creamy cm. Things can change over time too, and hormones varying will alter things. I used to have tons of ewcm a few years ago but I don't see much these days. I don't think it can be used as a reliable indicator by itself, but with other checks it can. What's your cervix position like? Sometimes at this point you will find your cervix is high and soft, but sometimes this won't happen until way after af was due. I usually find my cp is low and firm right before af.
Do you have any other signs?
With the test being darker, in theory it would be but in practice this can vary vastly! The hormone hCG won't always double quickly for everyone, so your tests may be faint for a short while and then you will see a darker line. For some this happens more overnight and they will see a darker test the following day. It differs with each pregnancy too. I would be more inclined to think if after a few days I wasn't seeing a darker line then it isn't a bfp. Give it time, and maybe it would be a good idea to start tracking your cycles and hormonal changes more closely?