WOW!! OP you and I must be cut from the same block!
I grew up in a household where I was the one expected to "hold it together" in crisis, and learned early on to push emotions as far from the forefront as possible.
I am the woman who runs to the bathroom to cry or has a standby smile ready to screw on when time gets tough. I have mastered the art of the game face, but I have found that philosophy will not work in this type (actually it should be in any type) relationship.
As hard as it is to swallow, vulnerablility comes with the territory, and acknowledging and expressing your feelings (and having the freedom and comfort to do so) as they happen seems to work better than allowing them to fester (I learned this the hard way this past weekend)
Take your time and ask for time. No one said this was easy, but I think this poly thing can be rewarding if handled properly.
Best of luck to you!