I feel sorry for you hon. It sounds like you don't have a real partnership, just a room-mate. Your feelings, your needs, your wants, are not part of the equation at all. Feeling stuck and being desperate to keep things 'As they Were' can also make it easier for you to lie a little to yourself about what is really going on. If I carried on like your SO my wife would have walked a long long time ago.
A gender therapist job is to help people make the right choices. Sure, everyone has fleeting thoughts, moments of fantasies, of life on the other side of the fence. Thinking that you may be trans is usually a lot different. There is big denial factor so the Yes I am... No I am not, is not all that uncommon. But add in all the other 'Odd' behaviors you are right to be worried. If the therapist doesn't hear the truth, but what is needed to get the job done, then there isn't much you can do about it. Besides some reality therapy with him. Put your foot down, get involved, to even getting out.
TBH - No sane person wants to be trans. Or, as my wife put it to me; "No one in their right mind WANTS to be a 50 year old woman". Well we both kind of sort of knew it wasn't that I wanted to be one, I fought the feelings for decades. The reality is I am a woman on the inside and always was, always will be no matter how hard I try fight it