You may want to speak to your psychiatrist, if you don't have one you should. Clenching jaws isn't a common side effect, it could be the anxiety, but then again it might not. It's important to see a pdod because they are experts in psycopharamcueticals. I've been on 8 mids in that class and none worked for long periods if they worked at all, that being Effexor, Cymbalta, Wellbutrin, those all made me seriously cranky and anxious. If you do have other presentations like for example; binge spending, serious irritability, rapid mood swings, it may be something else completely. So get into see a pdoc as soon as you can.