A 23 year old man comes to psychiatry outpatient due to symptoms of sleep disturbances and 'feeling low'. The symptoms staed 2 months back after he found that his girlfriend was cheating on him and was in a relationship with her boss. The patient immediately broke up with her. However since than he has been feeling sad, and repos that nothing makes him feel better anymore. The patient has stopped going to office and doesn't even come out of his room unless its absolutely necessary. He has not slept for seven days and has lost a couple of kilograms in last two months. During interview he said, 'i am a loser, my girlfriend chose a 50 year old man over me, there must be something seriously wrong with me, '. What is the diagnosis?