help!! idk if this is a miscarriage

i had a baby in february this year and he’ll be 10 months on the 29th. but a week or so after i had him i was in the ER because i was in sooooo much pain come to find out it was all from a piece of placenta left behind 🙄. i went to the bathroom earlier today and when i wiped i saw this. i thought it was part of my normal period and it was a blood clot but i took a picture of it anyway. the last time i had unprotected sex was thanksgiving but i took plan b the exact day and it was at the start of my ovulation. but the plan b made me cramp a lot and very nauseous. the week after on dec 2 i got nexplanon.

i was cramping really really bad last night it was maybe 9/10.

today after i saw this i showed my MIL and she said that’s not normal and made me call to make an appointment with an ob. when i went to the appointment, they said my pregnancy test was negative, the doc said it could be lining from my uterus, it could be part of the placenta from when i gave birth, or just a clot that was balled up that finally came out....

but she had no idea what this was.

so please help me figure out what this could possibly be. because i am in complete panic thinking i may have had a miscarriage and not have known i was even pregnant