I basically don't think there is any direct way to objectively know your gender identity.

To be honest I don't even have your level of awareness about what does or doesn't feel affirming to me, and my feelings are often self contradicting and unreliable. Sometimes I feel things clearly - like, I know I don't want body hair, or that I like curves generally. But it took me like 10+ years to figure out I like being curvy, but I don't like fat distributed in a male pattern - I thought I just hated being fat, but what I hated was having man-shaped fat.

Regarding pronouns, I was just used to what I had always been called and even now it can be jarring to be called by my "preferred" pronouns, so most of my life pronouns have just been a minefield with nothing feeling affirming or right. For me, they/them is the worst because it demands the most of other people and makes me feel the most awkward and puts the most attention on my gender, and it doesn't even feel affirming or "right". She/her is ideal, but I just feel like I don't deserve that ideal, and I definitely don't really think of myself as authentic or woman-enough to have she/her applied to me. So it can variably feel like affirmation or threat depending on whether I'm comfortable and passing vs insecure and unsure.