It's like identifying with anything else. You feel that this thing, whatever it is, is you. It describes you, it helps you understand yourself, and it's an important part of yourself. It's not your sole defining feature, but it's still important to you.

If you're wanting to make changes because "This isn't me" it's likely dysphoria. If you want to make changes because "I don't want people sexualizing me" then it's likely discomfort with society. The reason behind the feelings is something you have to dissect a little to figure that out. It's not necessarily easy, and no one else can look into your head to solve it for you, but it is something you can do.