I'm a little confused. You say early on that you "fall out of love" with people, but then later it sounds as if you maintain at least some feeling of love, you're just looking for more.
When you say "fall out of love" (if this description is accurate) what does that actually mean to you?
How do you feel about your current girlfriend and your relationship to her now, if you take out the worries about being involved with other people?
Then, when you say at the end that you "feel as romantically involved" with the new woman you've known for 3 weeks, what does that mean?
I think what I'm asking here is for a better sense of what you're looking for. Not that I really need to know that, of course, but it's helpful for you if you can articulate it for yourself.
I'm also struck by your comments about each relationship filling a bit of a void. I wonder whether relationships can truly fill it, and I think that might be worth thinking about.
Still, it seems like the concept and practice of polyamory might give you some comfort or self-acceptance, so I am happy for you that you feel you are figuring something out. The judgement you've been facing from yourself and others sounds like quite a burden.