I have been having constant brain fog, poor concentration, and I forget what I study. I wake up feeling exhausted even after sleeping and feel sleepy throughout the day. I have no motivation and feel like I have no control over my life. I recently failed an important professional exam, and since then these symptoms have become worse. Sometimes I also have thoughts of hurting myself, but I have no plan or intention to act on them and I am safe. What could be the cause, and what tests or specialist would you recommend?