Congrats on your BFP
Yes the doc tests aren't as sensitive.
When I started to spot i went to the doc and he did a urine test and it came back neg, however i already had 5 pos at home, i went straight from there to home and did another test (middle of day) and got another pos straight away. The blood test i had that day also confirmed that i was UTD.
Good luck with your BT on tue