Pregnant and birth control

So I'm pretty sure I'm pregnant. I was put on the pill for a month to control my last period but I think I just experienced implantation. I was taking antibiotics and with it being the first month on the pill I'm not overly surprised if it failed. My pill says to stop use if you suspect you are pregnant. What will happen when I stop? Will I still bleed from progesterone withdrawal? Or will I not bleed if I actually am pregnant?