Hi mnmom23,
Like others I'm hesitant to say too much because I think every child and every situation is unique. I think even within the framework of the ADHD diagnosis, there are so many other factors which may have more influence over a person than the attention piece. So here's my story - sorry it's so long.
Your son sounds an awful lot like the way I was in school. I spent a lot of time in my head, lost things, didn't do much school work, but I was happy in my world. One difference might be that when I was focused on a test or playing music, I wasn't slow. But given anything personally challenging, i.e. written reports that required organization and extended focus, and I felt overwhelmed. As an adult I have been diagnosed as ADD (with no hyperacivity). My understanding is that there are some "impulsive" things that I do that no one would ever really call hyper. For example, I move my fingers around (I'd run through piano or cello pieces with my hands, barely moving them, while in class. I also doodled - this is on another thread.) I haven't suffered many of the greater mishaps of adults living with ADHD like speeding tickets, car accidents, etc. If I had been the parent of me, I would not have opted for medication when I was young. I was an underachiever as I grew older, so in today's world, I would have considered cognitive behavioral therapy and possibly medication when I was an adolescent. Hindsight is great.
One of my kids is a dreamer who gets his work done; the other doesn't get his work done. I was never willing to consider medicating him to help him with school work, but around 5th grade he started to really feel badly about himself and was falling behind. Untreated ADHD puts a person at greater risk for depression and he seemed to be heading that direction. He started taking Vyvanse, a stimulant, in August, and the difference is amazing. He's as silly and creative as ever, but happier and more productive. I think the overwhelmed feelings are the ones that are dangerous.
As an almost 50 year old adult, I started taking a stimulant about 6 months ago. It's hard to describe the effect and I think everyone may have slight differences, but for me it gives me the sustained mental energy to follow an idea through to its conclusion, which in turn makes it easier for me to make decisions.
None of this means that your son has ADHD, or that he needs medication. In fact, if you're not pretty darn sure, I would not look to the diagnosis as an explanation for behavior. But, I am not and have never been hyper (in fact was so quiet as a child I was almost invisible) and I'm proof that there are introverted, non-hyper, non-destructive ADD people out there. And I love the combination!
It sounds like you're paying attention and if your son gets to a point where things aren't working for him, you'll know to look a little further. Enjoy the ride!
Benny