London I have had post coital bleeding quite a bit this pregnancy, usually 12-24 hours after rather than immediate. Last time (at 11 weeks) was a lot, I could feel it coming like a period catching you unawares. But all has been fine. I think just take it really easy and go gentle, it's probably a sensitive cervix and very unlikely to harm baby.
Had my 12 week scan today, due date changed by one day from 9th to 10th September. NT measurement was 1.5mm which I'm happy with, though we're going to wait for the full results of the screening before telling anyone. We've decided against a big announcement too, we're still a bit wary, much more relaxed and excited now than we have been, but don't want to make a big deal. So just going to tell people as and when we see them. We won't be hiding it - I'm my sisters bridesmaid in August, so won't be able to hide it then, that's for sure! 
Ginger I've tried the nub theory and have convinced myself it's a girl
but probably totally wrong or it will be a fluke!