Frustrations

My last class of the day--40 students--sat and blinked at me the whole class. And I know they understood me. I explained the activity about 1 million times in about 1 million different ways and yet they still just sat there in dead silence. Makes me want to throw something (not at them of course), just to see if they'll react. Then they complained when I went over time--we went over, dear class, because none of you could be bothered to give me one response to any of my many questions.

Does anyone else feel this way? Or am I just a horrible teacher?

I am starting to suspect I'm not a good teacher. At all.