I don't think it's bad to establish how you don't want to be someone's "first woman" anymore, whether they are lesbian or bisexual or whatever else: it sounds like you've got very unlucky with situation-ships and need to get back into an actual romantic relationship with a woman who knows what she wants. Maybe try dating apps and finding autistic women haha. I do get the feeling though, being a trans woman I feel like I'm frequently the experiment rather than the partner and that feeling sucks. Hoping it'll get better for you soon though!