It does sound like you need to have a sit-down, the three of you, and discuss wants and expectations with respect to "coming out" or "staying in the closet." Who can be told and why? Who shouldn't be told and why not?
As the "add-on to a married couple," I am technically in your position, so I sympathize with you. We are basically in the closet, so my two companions are known to everyone as "the married couple" and I am known as "the friend."
This was really hard for me to take in the early years of our poly relationship. It's not that I felt they were ashamed of me, it's that I wasn't allowed to show any public displays of affection to the lady of our ensemble. I had to act like "just the friend."
The perhaps disappointing news is that I just got used to it after awhile. It started to matter less to my what family/friends thought, and more what transpired in the walls of our own home. I have gone through several phases the last seven years. The current phase is, "indifferent about a bunch of things." I don't know if that's good news or not.
Still it would be nice if we could come out someday. I am waiting on my companions on that, since they are the ones who will catch #=!! from their families when they do come out. I may catch #=!! from my family but I am,
, indifferent about it.
You need to tell your companions that being "in the closet" is making you feel like "the dirty little secret." Try to negotiate and compromise and decide if there are a few people you can tell at least.
I don't think they mean to put you down. They are just scared of the repercussions of coming out. (And there will be repercussions.)
Hang in there, and talk this through with them a little at a time.