1pj - I was 6 weeks when it happened (had been overseas for 2 weeks so hadn't even had a BT at that stage). I got up to shower one morning and noticed some dried blood on my knickers. I freaked out and went to see my doc that day. Continued bleeding and it got heavier (like day 1 of af). Went for an u/s the next day and all they could see was this totally empty sac - couldn't see anything inside it, no yolk sac or anything. For that pg I didn't have any symptoms at all.

Good luck - I'm sure everything is going to be fine for you - it was just very early.