I've read on those fact sheets that it is a sign but what I've heard from other ladies is that it's not a reliable indicator in very early pregnancy. I know mine was soft from O until just before AF was due, then became firm and stayed that way until I was about 6 weeks (30dpo), and it moved around a lot too...it was very high one day and low the next. I think 7po might be too soon to see any obvious changes. My GP said it takes most women a few days after implantation to get a +hpt. Maybe/hopefully you ovulated earlier than you think? Good luck, I hope you get your bfp very soon!