Welcome! I'm new here, myself... it's a nice place, though. Those porpoises are very friendly!
I've never been exactly where you are right now - married and transitioning from mono to poly, but I do know what it's like to have to adapt to being poly.
Like most of us here, I was raised to be mono. When I was a teenager, I realized it didn't sit right with me, and it took me a very long time to figure out I was poly. The thing I most wish that I'd known then was that all the negativity that gets shoved down our throats about poly? Most of them are actually benefits or something that can be changed from negative to positive with a bit of hard work. It's all in how you think about it.
I hope that helps.