I personally would be more inclined to say what you wrote in reverse; not that "ASDs occur more frequently in this population" but that complex gender identity (and non-hetero sexual orientation) occur more frequently among people with ASDs. No direct correlation has been identified, but there is more and more clinical documentation of common co-occurrence (DeVries et al, and others). I've wondered if one of the consequences of our particular neurology and the way we think predisposes many of us to rejecting accepted social norms when it comes to sex and gender, at a very fundamental level. Whether we regard that as a good thing or a bad thing is up to the individual in the context of their own experience.
Welcome to AC, Pastel.
You may find that what's missing isn't
inside you, but external. Despite increased awareness of gender dysphoria/fluidity of late, there is still no socially accepted model or very visible identity group for your gender status. We develop as people in large part by finding mirrors of ourselves and our experiences in the communities/societies in which we live. Lacking enough of those mirrors, for critical parts of us, can leave us feeling a little lost and incomplete.
I see from your profile that you're 18. Most young adults have a good sense of their gender/sexual identity by the end of adolescence, so this may in fact be the "you" that will endure. I'm a heterosexual-leaning bisexual who identifies as more or less gender fluid. When I was your age, in the late 1980s, I had already gone through a few years of significant confusion for my sexual and gender identities because back then nobody talked about anything but binaries (gay/straight, cisgender/transgender), and only the "normal" side of those pairings was considered at all acceptable. While it's good that you're reaching adulthood in a much more enlightened time, those of us who live in the gray areas of the sex/gender spectra are still under-recognized and misunderstood, so the path to full self-acceptance remains very bumpy.
As for whether or not you should tell your therapist, I'd say that it's only worth doing if it's directly relevant to what you're seeing them for. If you are seeking therapy for things related to your previous diagnosis of a "gender disorder", then it would be a good idea to share your dreams
and the fact that within them, you are happy with fluidity. Those positive feelings, even just in dreams, can make it clearer to your therapist that you aren't necessarily looking to be "fixed" in any way, and could be very good fodder for a discussion about where your head is at on all of this. Just be sure that your therapist doesn't try to go down the path of blaming your "confusion" on your autism. It happens, and it doesn't end well. The last thing you need is to be told that your autism is complicating your essential self-concept. As you may have noticed here on AC, plenty of autistics know darn well who they are, even better than many NTs.
Keep sharing about this journey of yours with us. You've found a particularly empathetic group for this aspect of your life.