Actually, it really is ADHD and what you are describing are exactly the symptoms someone with ADHD would have. The fact that you are unaware of this means that your doctor (or someone) has not done a very good job at communicating with you. This is very sad because a child with ADHD really needs a whole different discipline schedule than a regular child. They also need a lot more help in school - hopefully he is getting that.
So since someone has not done a very good job of educating you as to what ADHD is, it is extremely important that you do it yourself - both for you and your son.
The easiest and most direct book to get a ton of info out of is, "The ADD/ ADhD Answer book." , by Susan Ashley. This book will give you not only ways to discipline your child, but more importantly ways to help him in school and life. I would also recommend that you read through this link on this forum for some fast information. http://www.medhelp.org/medical-information/show/2157/Attention-deficit-hyperactivity-disorder-ADHD
Feel free to post back if you have any other questions.