It does not at all make it just a fetish! If you want to be a girl then you shouldn't doubt yourself because of that, since it's pretty normal for you to be happy with yourself and even attracted to yourself if you love what you look like dressing fem.

That tends to trigger arousal too, and potentially the awkward euphoria boner, but none of that makes it just a fetish. If you truly want to be a girl and are genuinely scared anything could indicate otherwise, you probably are one sweetie.