I am sorry to hear you have been suffering from severe depression for 5 years. Have you talked to your family doctor about this? Also, have you considered seeing a counselor, psychologist or psychiatrist? This program is intended to help people with mild to moderate depression but the content can still teach you important aspects of CBT. CBT, Cognitive Behaviour Therapy, is a type of treatment that has the most evidence base in treating depression. CBT is what this program is based on. You can begin by reading the program but finding a specialist to help support you through this I think will be an important step forward. 

What do you think?