Bruxism has multiple causes but 2 most likely amongst them are Day to day stress in life and /or any malocclusion ( either natural teeth or cap & bridge that is faulty and needs correction).
Next Steps
Visit a dentist to rule out any such malocclusion. And evaluate yourself for any stressful situation when you start bruxing.
Health Tips
Night guard will prevent further breakdown of your teeth. But eradication of habit is utmost important. Following which rehabilitation of the tooth structure already lost is advisable.