Hi D., first I want to express my sympathy that your son is suffering this way. I know how depression feels, and like the commercials say, it really does "hurt." Anyway, I want to reinforce the previous mom's advice to avoid antidepressants if you can - there is a lot of research that says it can have a paradoxical effect in children, increasing the rate of suicide and increasing or causing suicidal thoughts. I am not totally certain on this, but if your son also happens to be ADHD, medications used to treat the condition can do the same thing to a child who is already depressed, so be careful.
You are very wise to see a psychiatrist. Make sure he/she is someone you are comfortable with since it is likely you will be with him/her for a while. Don't hesitate to change to another doctor if you don't feel right about the whole thing.
Finally, especially when there is a family history or if depression starts young, it may be more than just depression. This could be the hallmarks of other mental disorders such as bipolar or even shizoprenia. A good psychiatrist will help you flesh out what is going on. In the meantime, ensure that your son is active in school, has plenty of time to spend with friends, and has activities that keep him busy and distracted (church, sports, music, whatever he likes). Good luck.