vaginapagina | Help! Shedding entire uterine wall at once???

Hi all...
This community has been my go-to source for so many things but I can't seem to find an answer to this question. I found something kind of similar to my issue, but it doesn't seem to be exactly the same. I tried to explain it over the phone to my doctor's nurse but even she didn't know.

I have been on birth control since I was 14 because I've always had irregular, painful periods. I have NEVER had anything like this happen before. I am always on time, same day in my pill cycle, same duration.

I have been under an immense amount of stress lately and I thought that was the cause of my non-existent period. I was supposed to have started 3-4 days ago but only had some very light spotting and brownish discharge (usually this is towards the tail end of my period).

Today, I had some pretty bad cramping (which usually is the sign of my period starting), but I got so busy with work I started to forget about it. I went about my day as usual.

Got home, changed my tampon, and after wiping there was a fully in tact, piece of tissue on the toilet paper. It was almost like a sac or cylinder type of shape attached to a string. (Wide then tapers).
Literally, it was about 2 inches in length, maybe 1/4 to 1/2 inch in thickness, and was for sure pink tissue. It was definitely not a blood clot because after having a panic attack, I calmed down and cleaned it up a bit so I could explain to my doctor. It was like a cast of my uterus!

Unfortunately, my doctor is out of the office until Friday so it will have to wait until then and the only person that was available to talk to was the LPN in the office, who was not helpful at all. She made me feel like I was confused and didn't understand what menstruation was. Then she said she'd call me Friday once she can talk to the doctor.

Has this happened to you?? Should I be concerned? Did you talk to your doctor about it and what did they say? I asked the LPN if I should save "the specimen" and she said no, it's probably fine. I told her I would take a picture anyway.

Any help would really help put me at ease. I read on some other forums online that some girl had a uterine polyp that seemed to be described like this?? Another had an eptopic pregnancy?? (I don't think I could have been pregnant for the record. Had sex twice in last month, I take birth control, used condoms every time AND pull out -- my husband and I are as fool proof as possible)

I'm just scared... Help :(