Hi,
Thanks for the query.
Being on
contraceptive pills also, withdrawal bleeding is possible.
If you used contraceptive pills as per the guidelines, the possibility of
pregnancy is less.
The tissue you mentioned could be bit of endometrial tissue which might have came out along with bleeding.
If you missed any pill, there is possibility of pregnancy.
In that case, the tissue could be part of products of conception.
If you have that doubt, once go for urine pregnancy test.
If the test comes negative, the possibility of pregnancy is less.
If the test comes positive, once consult gynecologist, get examined and go for
ultrasound.
By this workup the possible cause for passage of tissue can be identified and can be treated.
Take care.