Cycle day 29, 15 days post IUI, BFN, on progesterone...continue it or stop it??

Tina
So i still am taking progesterone.... dr said continue 1 or 2 more days and retest. Today spotting is wayy lighter but test negative again. I will retest 1 more time but im still afraid to stop progesterone if i am pregnant.... or continue progesterone if its delaying my next period cycle