How would I know if I'm pregnant ??

Hi guys well I'm on bc pill been onit for three months now I went back to my nuse to get more pills an I asked her why I only got a Lil bit of brown stuff this month an I was due af two days ago an nuffik but so said I will not have periods on these pills an I don't have that week break thay said thay had to put me on the pills I'm on as my bmi was abit high but last night I was thinkin well say if thay did one day failed me how in the he'll would j know if I was pregnant as I never get that feeling I am ??