I have been suffering from chronic headaches for 4 years. Head MRI didn't show anything, psychotherapy hasn't helped, painkillers have no effect. Mouth guard didn't help either.

Headaches. Please go to a headache clinic at your local hospital. Also consider seeing a nutritionist who can test for food sensitivities. Look into biofeedback or clinical hypnosis (www.asch.net). I know it takes work and time to do this research but it can pay off when you find the solution. Peace and good health.