That's exactly how I'd describe mine. I can control it in certain situations like restaurants and phone calls now though. What I do is I conciously relax my chest and mouth area. I don't really breathe in deeply or anything I just don't let it tense up. When I feel the tension coming I just slightly breathe out and say the word. It's very difficult to do and the only way you can do it is conciously while maintaining monotone. So it's not a permanent solution unless you want to be an emotionless automaton