Implantation can take up to 10 days. so I would also say no.
I wouldn't think so...it's hard to detect at 5 weeks let alone at 3 weeks.
I don't think so, try calling your ob
I am not completely sure, but implantation can take several days, so I would say probably not. It seems like it is possible that you haven't even implanted yet. I would think that it too early to detect anything. Good luck!