BFP whilst on AF

Rachael β€’ Lost our miracle at 12 week after 7 years ttc 😒 and just lost our rainbow as it was ecptopic πŸ’”

So i started what i assumed was AF on 29/11. . . . it progressed enough to use yellow and green tampax. All normal so far. Then as AF went to dark red/brown, boobs didnt deflate. So tested and got BFP 7/12 and have had positive test every day since, BUT also still have dark red/brown AF. 15/16 days to date. HELP AND ADVICE? Been to doctor and she says 50/50 that i am prego or could have been chemical pregnancy/early mc. Surely i should have stopped bleeding and got negative test by now? With my mc in July, test went negative 3 days after i passed baby!