Maybe what is needed is not to make it about you and what you're not getting, but to find out what is going on with your unhappy partner and see if there is something bothering him, or some specific consideration he is looking for. Obviously, it seems he is going through something, and may be in emotional pain, but you seem to be taking it personally. Maybe a heart-to-heart among all three of you to see what he needs, and how you can all be happy again, is called for. It sounds like you aren't all communicating together, and you kind of sound like you are holding onto resentments. Maybe you have had enough and are ready to end it with that partner, but maybe there is also a more compassionate solution.
Originally Posted by nightrush
With this being all of our first attempt at being poly, their agreement was all or nothing... That is why i would have to leave the other one as well..
Well, to only have all three or nothing is just an unreasonable agreement from the get-go. Perhaps this is what needs to be renegotiated.
Also, people's desires have peaks and valleys. If you can find it in you to be more patient and empathetic, and allow for him to have his own natural progression in things, maybe you don't have to feel so slighted.