confusion after miscarriage around 3 weeks ago

i started my miscarriage on sept. 15, light bleeding, passed my baby (7+4 days in growth, but was around 10 weeks according to Lmp).

i didn’t bleed long after passing the tissue, and tested with tests down to a negative result. went to the ob, she did a urine preg test, negative. i’ve been feeling kind of sick. took a pregnancy test tonight. faintly positive ?

is this even possible? are these specific tests just super sensitive and it’s still left over? we started trying again literally when i was still bleeding and have had a looooot of sex lol

thoughts ? experiences ?