Fibromyalgia: Characterized by widespread musculoskeletal pain, fatigue, and tenderness in localized areas. The symptoms described, such as whole body aches and immense tiredness after a decent sleep, are classic for fibromyalgia, making it the most likely diagnosis.

Hypothyroidism: Can cause fatigue, muscle aches, and sleep disturbances. Although not as directly linked to whole body aches as fibromyalgia, hypothyroidism is a common condition that could explain the symptoms.
Anemia: Fatigue and muscle weakness are common symptoms of anemia, which could contribute to the feeling of whole body aches and tiredness.
Chronic Fatigue Syndrome (CFS): Now known as Myalgic Encephalomyelitis (ME/CFS), this condition is characterized by extreme fatigue that cannot be explained by any underlying medical condition. The symptom of immense tiredness after sleep is particularly suggestive of ME/CFS.
Depression: Can manifest with somatic symptoms including fatigue and body aches, making it a possible diagnosis for these symptoms.

Lymphoma: Although less common, lymphoma can present with systemic symptoms such as fatigue and body aches. Missing this diagnosis could have severe consequences.
Multiple Myeloma: A type of blood cancer that can cause bone pain, fatigue, and other systemic symptoms. Early detection is crucial for treatment outcomes.
Rheumatoid Arthritis: An autoimmune disorder that can cause widespread pain, stiffness, and fatigue. If left untreated, it can lead to significant disability.
Sleep Apnea: Can cause excessive daytime sleepiness and fatigue, despite sleeping for a decent amount of time. It's crucial to diagnose and treat sleep apnea due to its implications for cardiovascular health.

Polymyalgia Rheumatica (PMR): An inflammatory disorder that causes muscle pain and stiffness, typically in the shoulders and hips. It's more common in older adults and can be associated with giant cell arteritis.
Mitochondrial Myopathies: A group of disorders that affect the mitochondria, leading to muscle weakness and fatigue. These conditions are rare and often have a genetic component.
Ehlers-Danlos Syndrome: A group of genetic disorders that affect the body's connective tissue, leading to symptoms such as joint pain, fatigue, and sleep disturbances.
Porphyrias: A group of rare genetic disorders that can cause a variety of symptoms, including muscle weakness, fatigue, and neurological symptoms.