I posted a while back this same topic. I had become increasingly obsessed with this and could not settle. I managed to move past it (for a while) until yesterday my new midwife told me my dating scan coil be up to a week or so out. Now in devastated as I'd been told before that done at the right time they are never more than a couple of days in or out. Basically my last period was on or around the 20th August. I slept with my partner a few times between the 25th August until we reconciled properly in September. However after a drunken night in the 7th of September, I slept with a good friend of mine. On the 15th of September I don't a pg test and it was positive @ 2/3 weeks. My first scan put my due date @ 26 May 2015. Meaning I conceived on or around beginning of September (and I was sleeping with my partner at this time). But now after new mid wife saying it could be a week out I'm back to square one and I'm ill over it. Anyone any advice/experience please? Can a clear blue say 2/3 weeks only 8 days after intercourse? Does this seem more than likely paranoia and baby is my partners? Any advice would be greatly appreciated. Please no judgment. I hate myself enough as it is and this pregnancy is awful.