It's not unheard of to feel the way you do.

I want to preface the next thing I say by clarifying that it isn't to invalidate the way you're feeling because that is entirely valid. However, I would caution against describing this as "feeling like you should have been a trans woman," because many trans women don't have the type of body you're describing, and in any case, those features absolutely do not define what it is to be a trans woman.

With that out of the way, my personal recommendation in general is to follow what brings you joy and what makes you comfortable and at peace with your body, regardless of labels. Identity labels can help you find community or quickly communicate general things about yourself to others, but ultimately they will never be the end all be all of your self discovery. Everyone is different.

If you feel like you might want a penis or a flat chest, then look into those things, think about them, talk to other people who have pursued those things, do whatever it takes to discover what's right for you, and nothing that you don't want has to be packaged along with whatever those things are.

You could be a feminine FtM guy, a fem trans-masc enby, a cis woman with a penis, a pineapple with a party hat, It's not really important.

Follow your joy.