What Causes Passage Of Skin Like Tissue In The Menstrual Flow?

so I'm on the bithcontrol shot and I didnt have my period last month but I got it yesterday. today I had really bad cramps and when I went to the restroom I found that there was a 2 inch skin like chunk mixed in with the menstrual cycle. I search online and i saw some people have mentioned a miscarriage. Is it that or is it the Mucus blockage from the shot or something different. I'm wondering if I should be concerned or not