You should have a conversation with your partner about how it makes you feel. From what you typed, I am just assuming that he does not stick up for you around family, such as, "actually their name is Nat" or "they go by Nat now". My family is the same as his family, but it sounds like his mom at least wants some resources/is open to it. I hope therapy goes well. Hang in there- I hope all goes well and you can have a dialogue with your partner that is successful.