Please help 😢😢. Periods delay but tests negative!

Hi I am 15 days late on my periods. Have tested twice with pregnancy tests and they came negative both the times. Yesterday i had some blood spoting. My period are irregular. 15 days late is in consideration to the last period i had. My husband uses condon every time, infact he pulls out even if he is using a condon to be extra safe. I have never had unprotected sex. Am I pregnant? If yes what can be measures to avoid it.