Well, what you mean is that your sexual orientation (or, more precisely, your sexual "drive", since your orientation in itself doesn't vary) is fluctuant between not feeling any attraction, to feeling attraction.
First I'd like to ask what makes you feel the need or desire to have a specific name for that. Words to describe orientations (and genders) are multiplying widly since a few years, and LGBTQIAP issues seem to become identity issues and not political/social ones. And that's something we can think about.
It can be important for some to be able to "qualify" themselves and what participate to their identity, and I totally understand that.
But I'm wondering about that fluidity as you explain it, because in itself, "sex drive" (or, let's say, the spectrum of asexualitysexuality, because I know sex drive can be used to call something else) IS fluctuant and changing... For instance, have you asked yourself if this is about sex drive (libido) or your amount of attraction ? (a way to distinguish the two is that lack of attraction doesn't mean lack of libido. You could feel the ""need"" to masturbate but feel absolutely no sexual attraction toward people).
The second question would be : what do you want to do with it ? Is it for your personal identification ? In this case, isn't knowing how you function enough ? What you live is valid, since you're living it... whatever name you put on it. :)
Or is it to explain to others how you work ? And if it's the case, well.. what would you say to allow them to understand. Because you know, most people don't even know what demisexuality is.
To end this, greysexuality is a term to define the grey area between ace and sexual, which can be a way saying you're not one or the other, since you're fluctuant between those two. I don't know if it "speaks" to you, you can find more about in on forums like Aven.
What you call yourself belongs to you, and you could even create a word if you want.
I just think that a word that isn't shared and understand is useless (if everyone use their own very-specific word to describe their gender / sexual orientation / etc, since well, everyone has their own experience and way of living and feeling it, then we're all be alone, politically speaking, because there won't be any more ways to gather and have an impact... only ways to separate people... don't we know already that we're all different...? Why the need to say "hey, i'm even more different" when technically we describe the same thing :/)
Every variations of things don't need a specific word, or else, at the end, nothing will have any meaning at all.
So well, that's a little food for thoughts.