I stopped P4 at 8 weeks. I also felt that big tear across my tummy (such a weird feeling!) a few days before my 12 week scan. All was fine. If it makes you feel any more reassured, I did find a scientific journal article about the cessation of P4... and after about 8 weeks there is no difference in miscarriage rate regardless of whether you are on P4 or not. Congrats on making it to 10 weeks and I hope you see a beautiful little bub kicking away at your 12/13 week scan.