Hi I feel that there are different things you are facing in life, are you able to introspect the reason for your sadness and depression, this emotional disturbance is causing insomnia, lack of concentration leading to poor performance. I understand you are trying to overcome situation, but u can take help of experts in handle situation in better way. You can approach any psychologist in your place for better analysis and guidance. Take care.
Health Tips
dont stress yourself, have confidence, exercise, having social network and if possible sharing your feelings with loved ones might reduce your anxiety level.