I'm not sure if this is the right place for this...

So I recently started dating this girl(25) that's admitted to me she's poly.

I (m28) have been seeing this girl for a few weeks now. We've had sex multiple times and it's been great for the both of us as far as I can tell. We even went away for a weekend which was nice. I'm not really sure polyamory is for me but I'm not necessarily against it.

She didn't bring this up early on just kind of mentioned that she had an open relationship with an ex... Didn't really say that's her way or whatever. Part of it is that she says she's not necessarily into it already but wants to be open with me. All of this came up when I talked of being exclusive with her.

I'm not necessarily against the idea of being poly and I've been in FWB situations before so the idea isn't foreign. The issue is that I feel very strongly towards this girl. It hurts because I feel like I was trying to be real open with her, and she just dropped this on me. Part of me really wished she was more open with me to begin with. Maybe I wouldn't as fallen so hard for her, maybe I would have split more tabs with her(not that I regret that but I feel a little used)

I just don't know how to deal with this right now she's a lovely girl and I like her a lot, but part of me feels like she was disingenuous with me.

EDIT: Sorry if this post comes off as complaining, I'm just trying to understand this and these feelings. Maybe it's not the right thing for me but maybe it is. We only live once in this crazy world and why not experience it all.

EDIT 2: Thanks for all the advice everyone. The more I think about it the more I'm already a very open person sexually, and I don't see why I couldn't be more open with her. Going to sit down and really talk about all of this. If anything I'll find out more about myself.