What Causes Chest Pain With Numbness And Tingling In The Arm?

My son is 22 years old, 5' 10" and about average - 160-170lbs - weight. Over a year ago he had a short episode of 101 fever and rash which resolved. Shortly after (a couple of weeks) started complaining about severe chest pain and numbness and pain down his left arm. After many tests, x-rays and CT scan, it was determined that there was nothing wrong with his heart and could not see anything else that could be causing the pain. The pain and numbness (more like tingling) has continued and has now, within the last two days has spread to his leg. Lack of rest seems to exacerbate the problem, but even with rest it never goes away, and is now getting worse. We have an appointment with a neurologist, but it is not for 4 weeks. What could be causing this pain? Any thoughts?