I can’t tell...?

Today when I went to the bathroom when I went to clean myself I saw an oval like thing on the toilet paper. It’s about the size of a pinky nail I touched and it felt hard. I panicked inside because I’ve never felt something like this come out of my body. As I examined it more the more I just didn’t know. I went ahead with hesitation and squeezed the tissue a little bit and i felt a pop...I really don’t know. I even went ahead and put it in water to see if I can tell better but that didn’t help. It didn’t have a sack around it nor am I bleeding a lot just lightly (I believe I started my period yesterday or this is the miscarriage). I am 3 months postpartum. I even took a pregnancy test but it said not pregnant. Can’t anyone help me out please?