Uterine lining or miscarriage

I started the pill almost a month ago. Last night, 10.09.19, I took my first brown pill and I got home today at 4 and when I wiped, this came out. I had a tampon still in. It has veins and i had abdominal pain before. I don’t think I’m pregnant since I’m on bc, my boyfriend uses a condom, and he pulls out. I don’t know if this is normal since I’m new to bc or what, but I’m worried about it

UPDATE- second one