Hi, thanks for your help. Will try your suggestions and let you know how we went.
One friend of mine whose daughter suffers from severe anxiety has the family's large dog sleep in the same room as her daughter. Would this work in your case?
Since you claim your son has only been sleeping alone for the past four years, it does appear he might have some inherited trait of anxiety. If this not being able to sleep continues, you may require professional help. Anxiety issues are not the same as an anxiety disorder and if your son was able to function quite well before this event, then I suspect you're dealing with only "issues". But, that may require professional help (through intervention and/or therapy) to assist him to learn how to deal with these huge fears your son now has (which may disappear on their own or may not). If so, then contact your family physician and ask for a referral to a mental health specialist with experience in this area (and in working with children re "worries") as a child psychologist or specialized social worker.
Googling the term "anxiety in children" or "fears in children" or similar words/phrases should give more information re this topic. By the way, anxiety is a very common issue in childen and highly treatable. I wish you the best ....