Unexplained Itching On Arms

For sometime (Off and on for three years) I have had unexplained itching on my upper arms usually my left. It tends to happen only at night. It usually seems to be at a time when i might be under stress, possibly times when i have been having the person i date stay over for a period of time and might be feeling a bit trapped. the itching is usually somewhere from the top of the elbow to the mid upper arm. Sometimes the back of my neck. There is no sign of any outbreaks but sometimes small holes will open up from scratching. Went to a Doctor and he checked for obvious things such as scabies but was negative. It happens sometimes as i am going to bed or wakes me up in the middle of the night. I have tried things like antihistimes or cordisone creams to a limited effect. Tiger Balm helps at times. Last night was the strongest case so far on my right upper arm, but was sleeping alone and no obvious stress right now. Once it wakes me up I need to take a sleeping pill to go back to sleep. With no real external outbreak the main thoughts are psychological, toxicology or some internal function problem such as liver or kidneys. Am a 43 yo white male, 195 lbs, very little body fat, healthy, muscular and into sports