Could The Spotting And Tissue Passing Indicate A Miscarriage At 9 Weeks Pregnant?

I have taken a pregnancy test a few times all positive and i m three months postpartum. with this current pregnancy i would be around 9 weeks and some days. i started spotting with bright red blood, then brownish, also with a tiny bit of tissue passing about the size of a nickel. I was wondering if I may be having a miscarriage?