What Causes Red Blotches On Neck?

Red blotches have recently appeared on my neck. They are not itchy and are of varying sizes. What could they be? Also my urine has been bright yellow for the past couple of weeks.
I am 33 year old male, approx 6ft 5 inches tall, weigh approx 16 st 8 lbs. I suffer from Narcolepsy and take xyrem, dexamphetamines and sertraline to control the symptoms. I have taken this medication for approx 2.5 years and there has been no obvious side effects so far.