TMI!! What the heck is this?

TMI! During my period in May, I had this horribly weird-looking clot. I’ve been having periods since 2002, and I haven’t seen anything like it either before or since. I became sexually active in March, and my cycles were off for the next couple of months. In both March and April, I had a few days of very short, light, brown-colored bleeding, which is not normal for me. Then in May, there was this....thing. Is this normal uterus junk, or is it possible that I had a missed miscarriage or something? Ever since my May cycle, things have been normal.