Does one withdrawal bleeding from the contraceptive pill rule out pregnancy?

Does one bleeding from stopping birth control pills rule out pregnancy? Do you have to have several such bleedings, two or three to be sure that everything is as it should be? I already had two (always 5 days during a 7-day break) Do I have to do a test or bleeding in itself excludes pregnancy. For example, if you get pregnant before taking the pills, would you have been bleeding from withdrawal? (I mean confusing the inplantation with the period before taking contraception)