A 48-year-old female presents with an 18-month history of chronic headaches, fatigue, diffuse abdominal pain, and intermittent numbness in her hands. She has undergone extensive medical workup including MRI of the brain, nerve conduction studies, upper and lower endoscopy, and comprehensive bloodwork, all results are within normal limits. Despite these reassurances, she remains highly distressed by her symptoms and spends 3-4 hours daily researching possible diagnoses online. She keeps a detailed symptom journal, has visited seven different specialists in the past year, and becomes tearful describing how the pain dominates her life. She acknowledges the medical workups have been normal but states, 'The pain is real. I am not making this up.' Her daily functioning is significantly impaired: she has reduced her work hours and withdrawn from social activities because of fatigue and pain. Which is the most accurate diagnosis?