I don't think women "just know" - some probably do, I certainly didn't. With my first pg I had a suspicion around time AF was due, only because I noticed my boobs had developed stretch marks, but even then I didn't actually think I was pg. With second, I had no symptoms whatsoever, which is normal anyway, but I was sure I wasn't pg until I got the BFP. For me, the only way of "knowing" you are pg is to get a positive on a HPT or BT! Gotta have that evidence.

Bon