This came out of me earlier today.. what could it be?

So ive been on my period for about 2 weeks now. I figured its bc of the Depo shot. Well earlier today while I was at work I started getting really bad cramps, kind of like contraction feeling. I came home to take a hot shower hoping it would help my cramps. While in the shower I felt something coming out of me. I spread open my legs a bit and out came this thing. My clinic was already closed so I couldnt call them and they wont open until Monday. I picked it up and its real thick. It has a small hole on one side, so I stuck my finger in it and its like a bag-like thing. The day I got on the depo (12/13/17) was the same day I had taken a Plan B bc I had unprotected sex the night before (12/12/17)

Could it be that the plan B didn't work and this is a miscarriage? Or is it just some sort of tissue that the depo causes?

:::::UPDATE:::::

I went to my doctors today. He didnt bother even taking the thing from me to test it. He told me I could throw it away. There was no urine sample taken or anything... He did however request a pelvic ultrasound. So I will be going to get that done tomorrow afternoon. But I won't get any results back until a week from today.. 😒😕