I agree that ever day counts in the end if you want to avoid all of the pressure.
I do not believe that "They won't let you go past 42 weeks." is exactly accurate, you don't have to show up for an induction, but there will be awful and nasty pressure and you may face unwanted interventions if you go the hospital route. DD was 43 weeks exactly, delivered at home, but I was getting daily nasty calls from the backup hospital midwives, including being told I was killing my baby. that last week despite having passed a non stress test with flying colors at 42 weeks. Not what you want to hear when you are already anxious and trying to keep a peaceful mental attitude for labor.
Did you have any negative pregnancy tests before the positive? Any implantation spotting? Those date can help pin point when you conceived. I'm relying heavily on them since I ovulated at least 2 weeks later than usual (hence the "Surprise!") and my negative then positive tests back up my implantation day and my reasonable guess as to when I ovulated.
I'll give an example just in case it helps. My period was due 8/2 or 8/3 based on my usual cycle. I also had typical O fertility signs 10 days before and then what I thought were typical pre period fertility signs on the 8/1 and 8/2. I was so sure I was about to start my period I wore a pad 8/3 and 8/4. (This is why taking temps is really necessary if you are avoiding! I was not taking temps and only casually avoiding.) I've had 2 cycles in the last year or so go 6 weeks so I was not thinking "I'm pregnant." 8/16 I had implantation spotting, thought my period was starting. The next day my tooth paste tasted really bad and the light bulb went off. I tested every morning until I got a positive late at night 8/19. My other pregnancies followed this pattern. Implantation spotting and a positive 14 days post ovulation, never sooner. So I figure I ovulated on 8/3 or 8/4. The last time DH and I DTD was 7/31.
So now the interwebs know way to much about me.