My history of 25 years of tmj tells me that your problem is anxiety. During the day if I get stressed or anxious, I start involuntarily clenching and do a sucking in. As soon as I notice it, I try and stop, but it sure can be difficult. I have learned to try and keep my teeth apart and if the daytime clenching is real bad, I try and also keep my lips apart. It helps sometimes and sometimes it doesn't. If pain comes with all this, I usually have to take a vicoprofen.
Do you tmj or any of the symptoms of tmj (popping jaw, headaches, etc)? If not, great!! But you should definitely keep an eye on the clenching and grinding. You might want to consider getting a bite splint for night time. Also, ask you doctor if he might put you on an anti-depressant for a few months to see if this helps the teeth chattering?
I hope you find the help you are looking for. As a tmjer, please take very good care of your jaw and bite.
Carol