How can i know that i have stress or mental disease?

Stress: Stress is burdening any system more than it was designed to bear. Illness is when a system has been so burdened (stressed), that it fails to function as it is designed to function. If the burdens in your life are strong enough, your body (mind=symptom of brain function) will fail you. If your functioning/wellness is suffering, you are ill. Seek help. Talk with your md, sooner the better:).

Talk to a physician,: Psychologist, or therapist. It is helpful to start with a physician to rule out medical causes for your symptoms. Stress or anxiety can be effectively resolved with relaxation training, perhaps with the aid of biofeedback (www.Bcia.Org or www.Aapb.Org), and cognitive/behavioral therapy.