What do I do if I worked out for four hours yesterday and now my whole body is so sore that every move I make is excruciating?

Anti Inflammatories. 800 mg of Ibuprofen immediately following a work out can help reduce delayed onset muscle soreness. Always clear this through your personal physician as these anti inflammatory medications are not appropriate for people with certain medical conditions.
You overdid it. Your muscles are sore from over exercising. It will usually improve over next few days, but it is very important to drink very large amounts of fluids so your kidneys can clean your body of a chemical called myoglobin that gets increased from muscle damage. If you don't ur kidneys can literally "plug up". If urine dark (red), then see your doctor right away. Take Motrin for pain.