I get like that from time to time--I go flat in my affect when I "should" be expressing my misery, especially in therapy. Because I've been with the same therapist for so long, I can comment directly about it and he gets it. He has learned to listen to the content when the affect doesn't match up.

When I get so I'm unable to express the stuff "underneath," I write it down and take it to therapy with me. That way the information gets communicated, and then we can work on it.