What Causes Discharge Of Blood Clots With White Tissue-like Discharge?

Hi, I got my period 2 days ago, and yesterday I noticed a huge chunky discharge of blood clots and white cord-like tube that consisted of a tissue, it seemed, and was about 1/8" thick and 2 1/2" in length. I tried to move it around to study it and it seemed like a plain sheet of tissue that has been rolled in a tube. I took a picture of it and am not sure if it is serious or just a side effect of birth control or something else (I started birth control 2 months ago, the brand is Natazia). There was no extreme abdominal pain or anything unusual except breast tenderness.