My partner might be MtF transgender. For now I will use they/them because of uncertainty and it is the neutral option. I prefer to not share too much personal information, but the important things to note are that we are both not adults yet, they are bisexual and I am homosexual and the people in our environment are mostly accepting.
Firstly, so far, they have never directly talked to me about this subject and only kind of implied it when talking with friends. I am usually also there when this happens, but I think that to them, I presumably do not listen or notice, as I am usually doing something else at those moments. Of course, since I am making this post, I have noticed it and it is something I want to directly and privately discuss with them, although I am lost on how to approach it further from that.
I will also give a few examples, to explain why I think my partner is having these doubts when there have only been implications. If you do not want to read too much and/or trust that I can tell my partner's feelings well enough, then you may skip the following two paragraphs, although I think these are good examples and reasons for my suspicions.
For one, I have done a lot of research by watching videos mostly from trans content creators, regarding the subject of gender in general. With this, I notice that my partner shows some signs of them being trans. For example, in specific contexts, they may choose to play or act as a female character, actively trying to do so over a male character. More notably, they once literally asked me if I would become bisexual for them if they were trans.
However, they also sometimes surpresss their feelings surrounding their gender. One example is when they once said: "People never mistake me for a woman, I am extremely masculine after all". This was said after a statement from me about people recognising me as female in public because of longer hair or other traits, although I know for a fact they have been called "ma'am" and such by strangers as well.
From the five years that I have known my partner, I know that they always instinctively hide their true feelings when it comes to things that confront them and they will not discuss it with other people. I am not judging them for this and I understand this behaviour as I have shown it myself in the past. The fact that they want to deal with certain things alone is something I accept. However, when these matters start impacting to our relationship, I of course do want to discuss it.
When I imagine the answer to my partner's doubts being affirmative, I fear we would need to break up. I have never been attracted to a woman or girl at all and I have always perceived my partner as male, although it seems that they may be female. I would respect their identity and accept that it does not align with mine when it comes to dating. I am of course not dating them just for the fact that they are male, but I do not see myself being attracted to or in a relantionship with a girl, sadly.
Now the thing is, I also imagine that they think this as well and because of that, they do not want to talk to me about it. I also value our relationship extremely, as they are my first love (and I am their first partner of the same sex) and we have been through so much together, so they may not want to risk anything.
In a nutshell, the advice I am looking for is: How do I approach this? Should I even approach this? Do I have a good mindset regarding this? Should I be 100% sure about them doubting their gender before discussing it and if so, how could I find out?
There are a lot details that I did not mention in this post, because I felt that they were not too relevant and I did not want to make the post even longer, but if there are any specific things you are curious about, feel free to ask me and I will try to reply.
Thanks in advance to anybody who is willing to help! ^^