Retained placenta?

I had my son August 15th via C-section. I bled lightly for 6 weeks and never had any major cramps. The last week of September I got on birth control pills. My bleeding stopped for a week, before restarting for almost 3.

October 6th, this came out attached to my tampon. It felt like a rock/fruit pit. In my PPD haze I didn’t bother calling my doctor, since after some googling I read that sometimes weird things happen postpartum.

Anyway, I’ve been spotting like crazy on and off without a real period. I’m not sure if it’s because of the birth control pills or what. Anyway, I’m still having some minor cramping.

Could this be a piece of my placenta or something else? Should I call my doctor tomorrow? I’m worried there might still be something still inside of me and I don’t want an infection or something horrible to happen.

Thank you.