I've found that I personally become constipated (creatively speaking, of course) when I've made a mistake somewhere in my story, and while my subconscious realizes that mistake, my conscious mind is too slow to have caught it yet. Then, the churning begins. The subtle pain that begins to grow. The steadily rising nausea. A tightness in my innards that just won't go away.
Unfortunately, there is no laxative for creative constipation, no prune juice, no fiber regimen. There's only patience and hard work... and perhaps a much-needed distraction. Hopefully, these things will eventually get the creative juices flowing again, and that...blockage...won't be a problem. I realize it isn't a pleasant visual, but really, writer's block/creative constipation isn't a pleasant experience.
If you're a writer, you know what I'm talking about. Don't be embarrassed. There's no shame in it. Even those who don't get creatively constipated understand the basics of constipation itself. Why? Because, as I said before, we all get constipated sometimes.