This is a new one for me. I don't feel stressed and I know it's not drug related. My dentist though says it possibly is stress. But could it be a habitual thing? My jaw now aches from the sporadic clenching either way. And yeah this is my last stop before going out to get a second medical professional opinion.
Ask your dentist about a bruxism appliance. They range anywhere from $200-$500 depending on your location and dds fees. Also walmart or probably any similar store carries generic mouthguards for around $30-$40. The difference is your dentist will make one that fits your mouth exactly.
I have TMJ, which is where I clench my jaw at night. I would just go to a drug store and buy a cheap sports mouth guard. It's the same thing I paid 500 for and it will keep your jaw apart enough to keep you from grinding.
There's some kind of device that helps with this, I don't remember what it's called, but ask your dental care provider about it. I don't believe any type of medication can help this, but the best I can say is talk to your dentist.