I strongly suspect your son is suffering from anxiety - social anxiety and/or selective mutism. I might suggest you google the phrase "anxiety and children" or "social anxiety and children" or "selective mutism" or words/phrases similar to those. Then I think you need to visit your family doctor and ask for assistance. If he/she is unable to help you, ask for a referral to a medical specialist with experience in anxiety disorders as a child psychiatrist or child neurologist.
Anxiety is a very common mental health issue in children; however, it does become more difficult to treat as the child gets older. Your son is in the "older" category. Please seek help immediately as your son will not outgrow this nor will it go away. But, there is help out there and treatment (which usually consists of intervention, therapy and possibly medication) can make a huge difference in the life of your son. I wish you the best ....
I appreciate your advise, I am seeking a child psychologist to address these problems that we were hoping would just go away, but I see now it won't. thanks again, Dawn
My Granddaughter is very shy and anxious. When she was first starting to talk she was fine. After a couple of years she stopped talking to everybody except her Dad, Mom, and myself. Sometimes she will talk to Grampy. She won't talk to any of us if anyone else is around. Finally they are getting her to speak up enough so they can hear her. If you try different things with her she cries like her heart is broken.. She rarely talks to her best friend. She is now 11.