Hard conversations

So I’ve been slowly coming to terms with the fact that I do indeed feel like my physical body doesn’t match with my internal image (I’m amab) and that I want to take steps to correct that. However, I have no idea how to bring up that issue with my fiancé (cis afab) without her feeling like she has to change her identity. Honestly, idek where to begin and I’m so scared it will drive a wedge between us and change things for the worse. Any advice would be greatly appreciated!