My husband is bipolar, his father is, his grandmother was, an uncle of his was... His one brother is schizophrenic the other brother is just wierd and mildly uses drugs.
So far none of my children show signs but we're being vigalant. And, horrible as it is, a childhood friend of mine's younger sister, who was 10 at the time and suffered from depression committed suicide at age 10.
If your son is bipolar then your child certainly can not help himself and he needs help. Contrary to Tom Cruise statement, depression and bipolar is a medical disease and drugs do help - but and I can't stress this enough- you need a psychiatrist coupled with the drugs. One with out the other won't help.
The bipolar person still needs to talk thru what is happening to him/her, understand that is body chemistry and not their own fault and he/she needs to learn how to deal with the 'triggers' - the things which can trigger an up or a down - and identify those triggers. A great book on the subject is Anne Sheffields' "How you can survive when they're depressed" (It talks about depression and bipolar people.)
Do be persistant in getting help - if it is bipolar it won't fix itself and will just build more and more trauma and pain for your son to deal with and have other repurcissions as you already see with problems at school, having freinds. As he get's older its typical for undiagnosed kids to 'self medicate' which is to seek release thru alcohol or drugs..and to have severe finacial problems as they excessivly over spend when they are on the 'high'.
When we finally recognized what was going on with my husband it took us almost 2 years to get the right balance of drugs - to control the ups and downs. But now for 5 years he's just like 'normal' and for the past 2 years has not needed to see his psychiatrist - he just uses meds. And he's so mad as his family for not admitting bipolar existed in his family and for letting him self distruct for most of his life.
If your son is bipolar you can spend all your time teaching him 'right' behavior to no avail - he really can't help himself. My heart aches for you and your son.