Well, as you know if this is your third child, when a medical person tells you that you are "x weeks pregnant," he or she is not referring to the presumed date of conception, but to the presumed first day of your last period. If you had sex about four weeks ago, that would make sense. His sperm would still be in your system for 5 days after the sex, and you would have ovulated at the "3 week 3 day" point by the medical count. Plenty of chance for it to be him from the visit 4 weeks ago.
My husband works away and we only had sex that once 8weeks ago And then again 4 weeks ago, so I just don't know how I could be 5 and a bit weeks pregnant, I should of wrote that in my post as well and I'm still bleeding quite heavy, I wouldn't call the pain terrible it feels more like period cramping
You might have had a miscarriage and now are on a new pregnancy, thus explaining why you think you are at 8 weeks but are really only at 5. This would explain a little light bleeding 3 weeks ago also.