The Story That Broke The Camel's Back

I think, unfortunately, in this title, I'm the camel. But I've got this new story that I thought I'd have plotted out by now (yes, even though it's only been what? Six days?) and I can't seem to get past the first act without realizing what a jumbled mess it's turning out to be. This isn't how the machine of writing I've built is supposed to function. The more you do something, the easier it's supposed to become isn't it?

Let me give you the elevator pitch.

A couple, in the midst of planning their entire life together, decides instead that they need to break up. They also realize that the reason some people slide into marriage so easily is because they have the transition of an engagement. So they take the same principle of easing into their breakup. Their friends, rightly, go nuts, but parties, unproposals and all, they're going to have The Unengagement.

I put the last part in italics because that's the title of the movie.

But you see my point. It should be a fairly easy story to tell. I've broken a "hitman's last job" story and a brand new superhero's origin story this year. A(n) (un)romantic ensemble comedy should not be giving me this much difficulty.

So that's what I have. Is there anything you'd like/expect/want/not want to see in a movie like this?