I broke out with red like sunburn rash today all over body, took 50mg benadryl (diphenhydramine) and doesn't seem to help. two days ago i was in bed all day because every joint in my body hurt and had no energy or strength... not sure if it's related.

Viral Illness: If your rash is red, raised, and itchy you could be suffering from acute hives (urticaria). Hives is a common manifestation during are shortly after a viral infection which it sounds like you are suffering from. Try treating with OTC nonsedating antihistamine like Zyrtec (cetirizine) 1-2 per day and symptomatic management (increased fluids, rest). If rash not responding see doctor to have evaluated.