ON BC, you do not bleed out ANY tissue, that is because birth control ensures that your lining is VERY VERY THIN.
The ONLY reason you even get a 'period' on the pill is because you stopped taking hormones, it is simply a 'withdrawal bleed' from lack of hormones.
BLEEDING on the pill is NOT a sign of pregnancy.
I am a health care professional
WHAT is it a sign of? WELL, WE do not 100% know. What we do know is that almost ALL women will have this at some point in her "pill" years, and it is common.