Hi, I'm hopeing I can help....if Dr is saying you are five weeks then you would have gotten pg 3 weeks ago.....the first two weeks you are not technically pg as its the first half of your cycle and you wouldn't conceive til after ovulation at around two weeks but they count from first day of your cycle.
Your first scan will give more exact dates as to how far along you are. I'd expect the Dr to take the bleed you had with the clots as a cycle and that the spotting on may 20 was implantation for the bfp on the 29th.
This would be my guess anyhow x congrats and good luck xx