My son has an itchy red rash that turned dark black or brownish color he has been this way for 2 weeks now. its all over no other symptoms but fatigue?

Fatigue: Your child should be seen ASAP by your pediatrician or possibly a pediatric hematologist. The dark spots may represent black and blue marks that should be evaluated with at least a complete blood test

See a dr: Rashes are difficult to diagnose without seeing.If this is ongoing see a dermatologist or maybe your internist because of the associated fatigue.Many systemic diseases have rashes associated with them.Get checked.