Welcome to our forum.
I am just guessing "yes" on your survey; it is really up to you to decide whether you are poly. We are speaking of polyamory in an orientation sense; there is also poly in practice, where you are living in a poly situation. I also think there are degrees of being poly, but that's my point of view.
As far as telling your significant other, you could try the following link:
Spend some time reading the various threads on this site, and post any thoughts or questions you may have. It's good to have you onboard.