Impaired concentration, anxiety, worry, forgetfulness, and negative thoughts are mentioned by you here as the prominent symptoms that are causing distress to you. All these symptoms put together may amount to a depressive episode or an anxiety related disorder. My suggestion to you would be to seek a consultation with a psychiatrist, who will assess your condition in detail, and then a comprehensive management plan can be made. The management of such symptoms is likely to comprise of psychological intervention and medication to relieve your distress and optimize your functioning. Hope this helps you..