I started taking B6 a couple of months ago as my LP was 10-11 days. 100mg is the correct dose to take. I stopped it because my cycle went from 32-33 days, to 50 days on the next cycle....I am almost positive this had nothing to do with the B6, and more to do with the fact I was on the pill for 15 years and my hormones are taking a bit longer to settle down, but at the time, a kind of freaked out a bit. Last cycle was 36 days and I am going to start the B6 again next cycle. I am not sure if it affects CM. I suppose there would be no need to continue it once you fall pregnant, but this is a guess on my part. Hope this info helps - I know heaps of girls who swear by B6 to lengthen their LP's. xx