Fibromyalgia: Characterized by widespread musculoskeletal pain accompanied by fatigue, sleep, memory, and mood issues. The pain in fibromyalgia can be migratory and severe, lasting for days, which aligns with the symptoms described.

Polymyalgia Rheumatica (PMR): An inflammatory condition that causes muscle pain and stiffness, primarily in the shoulders, hips, and neck. While it's more common in older adults, the migratory nature of the pain and its severity could fit the description.
Viral Myositis: Various viruses can cause myositis, leading to muscle pain that can be severe and migratory. The duration of the pain can vary but often lasts for several days.
Inflammatory Myopathies: Conditions like dermatomyositis and polymyositis can cause muscle weakness and pain. The pain can be migratory and severe, although these conditions are less common.

Acute Intermittent Porphyria: A genetic disorder that can cause severe, episodic abdominal pain, neurological symptoms, and sometimes muscle pain. It's crucial to consider this diagnosis due to its potential for severe complications if not treated.
Vasculitis: Certain types of vasculitis, such as giant cell arteritis or polyarteritis nodosa, can cause severe, migratory muscle pain due to inflammation of blood vessels. Missing these diagnoses can lead to serious complications, including organ damage.
Lyme Disease: Caused by the bacterium Borrelia burgdorferi, transmitted to humans through the bite of infected black-legged ticks. It can cause a wide range of symptoms, including migratory muscle and joint pains, especially if not promptly treated.

Ehlers-Danlos Syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. Some types can cause severe, migratory joint and muscle pain.
Mitochondrial Myopathies: A group of conditions caused by mutations in the mitochondria, leading to muscle weakness and pain. The pain can be severe and migratory, although these conditions are rare and often present with other systemic symptoms.
Statins-induced Myopathy: Although not a disease per se, the use of statin medications can rarely cause severe muscle pain and damage. This is a consideration in patients on these medications, especially if they have recently started or increased their dosage.