TMI brown/clear mucus? Help!

Hey girls-

I know this is TMI, but just wondering if anyone has had this or know if it’s normal? I’m getting my period within the next 3 days. I’m on birth control and take it on time every day. Tonight after peeing, I looked in the bowl before I flushed and noticed a small clear crescent shaped mucus piece with brown on the end in the bowl. My stomach literally began to hurt immediately after. I’m thinking it’s just old cervical lining shedding? Idk I thought it was weird...wanted to see what others thought? Thank you!