Linea Nigra first sign of pregnancy?

I’m only 6 dpo but as I got out of the bath tonight I noticed have a visible Linea Nigra. I have had two previous pregnancies, both the Linea Nigra formed late first or early second trimester. I’m just wondering if a Linea Nigra happened to be the first sign of pregnancy for you? Have you had this line show up and not be pregnant? We’ve been TTCing for ten cycles now and seeing this tonight was a really confusing sign! I’ve been very crampy which is always normal for me post ovulation. No other pregnancy symptoms.