This sounds familiar!
I distinctly remember the moment when that "other" voice finally disappeared. It felt like a "pop" in my head, a moment of self-sacrifice. At the time. Now I realize that the voice was never real, just something I had constructed back when I was a little girl. (They also wrote me a really condescending letter before they left. Hmmph!)
Anyways, yeah, it's normal to go back and forth internally for a while. It's a daunting journey -- if anything, the presence of that voice bringing up doubts and fears means you really know what you're about to face. It's an indication of sanity, I think!
Transitional steps will clarify the dialogue. See how you respond to HRT. See how you respond to be gendered correctly in limited compartmentalized social areas, like the therapist's office and support group, regardless of appearance. See how you respond to voice training, especially once you start getting results. See how you respond to electrolysis (really, do zapping and voice now, woman, 'cause it takes so long) and how you look without facial hair. You can do all this without going full-time, even without coming out to the majority of your social world.
Transition is a process. It might seem haphazard and messy, but it can really bring into focus what it is you really need. And need will win out in the end. Need can't be "reasoned" away.