Well done, I'm sure that must have been a difficult post to write. Thanks for putting trust in us to listen and support you.
Are you already seeing a Psychiatrist/Psychologist? It would be good to speak with them about your thoughts and feelings. It must be hard and confusing to feel the way you do.
I guess if you're in a relationship being bisexual isn't really a huge concern, as long as you love your partner and want to be with her. I think it's something you could raise with her, especially if you have no intention of exploring the possibility of being with a man. Many of my friends are bisexual, so I do understand that being bisexual doesn't mean that you would prefer to be with one sex over the other, only in choosing your partner your heart and mind don't discriminate against gender.
With regards to your desire to be female, I think this is something you will want to think long and hard about (not implying you haven't over the past 41 yrs). What will the benefits be? What will the consequences be? How willing are you to go through the consequences? Do the benefits outweigh the costs? This is your life, and so ultimately it's your choice. Will you regret spending the rest of your life as a male?
I hope this has given you some things to consider, I also want you to feel comfortable to continue posting your thoughts.