What Causes A Sponge Like Tissue In Bleeding?

Hi, im 17 years old. Im sexual active. Im about 5'7 and weigh 135. I had a threathed miscarriage. I woke up this morning to what feels like kicking. I read that it can be gas or poop. But I dont believe it. I heard about having twins and one dying. When I bled, I saw a sponge like tissue. And a clearish and milky.. I have no idea what it was. I thought it may be what holds the baby. Im confused, and there are no answers.