You are not alone. I have been through this, too. It is horrible and shaming. Two years later I am still shamed, though I know I did nothing wrong.
I never have found out exactly what happened. This is a phenomenon that hasn't really been studied. It used to happen often, before u/s were common.
I went to an RE, while I still had symptoms. My belly had shrunk a great deal, but I still looked pg. He blamed it on breastfeeding my toddler (even though my milk had decreased dramatically, and, in fact, dried up completely the week after I saw him, and even though that is an asinine conclusion). All he could talk about was "getting [me] pg".
I would love to believe that I just wanted a baby so badly that my mind created that pregnancy for me. It would be so much easier if I could believe that. Then there was no baby, and I just was messed up in my mind a bit. There is no shame in going through a hard time, mentally.
But I do not believe that fits with what I experienced. Here is my theory. It's the closest I can come to understanding what happened to me.
Please DO NOT READ if you are sensitive to a frank discussion of m/c, etc. This is graphic and straightforward. I do not wish to hurt any mamas.
I think that there is a real, physiological basis for "pseudocyesis". This problem is leftover from a former era when anything wrong with a woman's body was written off as being "all in her head", for the most part. Then take into account the fact that doctors and mw's were fooled into believing women were pg, who lated produced no babies. They had no investment in investigating this further. What an embarrassment to them! Nor is there any investment in that now. It doesn't happen in the general community...usually... only in the UC community.
Why is that?
Because we don't get u/s's. This is what I think. I think the baby dies early in pregnancy. This happens all the time, to lots of people. And sometimes they know, and m/c right away. And sometimes they find out weeks after the baby had passed, but their body does not initiate a m/c. So their OB or mw presses them to have a D&C or D&E.
But what happens if you *don't* get a D&C?
The body of the baby starts to break down. This actually begins very quickly after death. The mother's body begins to absorb the material left from the body. Sometimes this causes an infection. But I believe that sometimes, the baby is fully reabsorbed into the mother's body. We know this happens. We've seen it MANY times with a twin that dies early in a pregnancy, now that we have frequent u/s. It happens in lots of other mammals...sheep, dogs, rats.
I believe that something about the process of reabsorbtion messes up your hormones royally. My hormones were a mess for a very long time, including my thyroid (just like when people lose babies at the end of pregnancy, babies that they see with their own eyes). Because of this, I think that the body does continue to behave as if pregnant.
It doesn't explain how I and others heard a heartbeat in the same place (I wouldn't say where I'd found it, and someone else found the hb in the same place). It doesn't explain how others palpated baby's form from outside my belly, in exactly the same place I felt it. (I told you, it would tie up more loose ends to just believe that I had some kind of temporary loss of control over my own mind).
Think of this: do animals who experience this go through it due to their intense longing to have babies? Seems a bit unlikely, yes?
Be gentle with yourself, and know that, even if no one else understands, there is someone out there that believes you, 100%. You do not need to be ashamed. I am sorry for your loss.