Hi, I am sorry about your friend and can understand your emotions. You seem to have developed negative thinking as a result of the stress which is resulting in your feeling guilt and worthlessness of life. All these are suggestive of underlying depression. I feel your condition demands immediate attention and you should seek a psychiatric consultation without any further delay. Treatment with anti-depressant medications like escitalopram or sertraline will be helpful in controlling your symptoms and will help you see the brighter side of life. In addition, you should consider exercising daily. It will help you relax and feel better. I do hope that I was able to answer your query. Best wishes.