As the old saying goes, you can't be a little bit pregnant -- you either are or you aren't.
That is NOT how it is with poly. There is a whole spectrum of psychological configurations, a whole range of behavior preferences.
One guy on the forum (MonoVCPHG) i's really monogamous but loves a poly woman, and he writes with great understanding about poly and relationships. Others have intricate webs of lovers and significant others.
I can only write in detail about my own feelings: I don't feel much or any possessiveness or jealousy, and I'm very happy that my dear GF finds the love she needs from her husband as well as me and others. But I have no real drive to love many different people myself, though I have woman friends I care for quite a lot.
You mileage will always vary.
So the question of whether you are poly may never have a clear answer. You are what you are, and it fits somewhere in the spectrum of normal and loving human behavior.
The main thing is to do what is healthy and good for you, and healthy and good for your partners and friends. Grow when and where you need to; take care not to hurt or damage others.