Whether it's bad or good is relative to your experience.
That being said: First, I think many (myself included) would suggest what you're doing is a form of tulpamancy. I would say you're creating a servitor whose purpose is "give me a pleasing image to view and imagine myself as" and by invoking it constantly, gradually feeding it energy until it will become self-sapient and develop a will of its own. This can be a positive exercise, but you should probably write up a bio for this alternate personality now while it's still malleable and cultivate it into a beneficial ally before it becomes fully self-aware and goes rogue. Most of the tulpa memes are just that, memes, but they're still quite real if you buy into them so it's best to pin down your subconscious ahead of time and say "no, we're playing nice with each other, here are the rules".
Second, you won't get what you're attached to as long as you're attached to it. See, you think what I mean there is you're attached to this form, but what I actually mean is you're attached to desiring this form. As long as you want this form, you aren't going to get it, because wanting the form is what defines you, not having it. When you don't care as much, you might get thrown a bone. Better would be to consider why you care about the form in the first place.
>What am I doing, is it spiritually productive?
Yes, because you're exercising your mind's eye, which is an atrophied muscle in most people. It's beneficial at the bare minimum because you're practicing using your imagination.
Oh, and if your alternate/imagined self is a girl and you're a boy, you might want to consider joining the trap cult and worshiping the trap god. He'll give you boons at relatively low cost, and worship to him is a good way to practice meditation, so he wins from feeding off of your energy and you win because he gives you power in return for prayer. Everybody wins when they worship the trap god.