What Causes Piece Of Skin In Menstrual Flow?

Hello,

I just got my period today in the middle of the night and just about 2 hours ago that I went to change my tampon I saw this little thin piece of skin. It was really thin but strong and it felt as if it had tiny tiny holes or bumps. I know it's not blood clots because I get those all the time and this looks way different than that. I'm on birth control pills but Im really careful with them and take them at the same time every day, this is my -reminder pills- week.



Can anyone help me, please?



Thank you.