That's a serious amount of resentment that you've built up! Like GG said, you've articulated your feelings loud and clear. And it seems as though you've told them about your dissatisfaction without receiving the support and reciprocation that you need.
Look, I think the ball is in their court on this one. I understand that they may be acting a bit selfish in order to patch their relationship, and they should see this in themselves - but why aren't they communicating better with you to relieve your frustrations?
They should either:
Explain to you that this situation is temporary, and they should be spending more time with you as a 3some. This way they still spend time with each other but at least make an effort to tend to your needs. They should get a babysitter and take you out more often.
Or, they should be honest and tell you that they have serious problems and need time alone - without you. It's tough honesty, but it allows you to make a choice about weather or not you want to stick around. Are you in a position to leave or do they think they have you as a captive live-in babysitter?
Either way at least you know where you stand and can take back control of your future.
Take the risk of thinking for yourself, much more happiness, truth, beauty, and wisdom will come to you that way. - C. Hitchens
Me: Male, bi, 48, flexible