Cola, I don't know your personal situation so I can not provide specific advice. However, there is no need to medicate your child unless you have had an appropriate and thorough assessment. You also need a clinician with whom you feel comfortable and who will provide a prolonged and supportive relationship. If the diagnosis of ADHD was borne out and medication prescribed it would need monitoring and adjustment and careful ongoing management.
How do you find a new paediatrician? As I say I don't know the specifics of your insurance or the services available to you but it pays to do some research, ask some questions and seek advice.
Others on this forum may be able to advise more specifically if you can narrow your location at all. Otherwise, hit the internet and look for specialists in your area. You mention your brother has ADHD, any information to be sourced in that regard for specialists in the area?
Thinking more broadly, in case as you suspect this is not ADHD, look for gifted specialists and neuropsychs who could perform assessments. Is there a University or hospital backed clinic you could access.
Doing some broad research on your own doesn't hurt, which I am sure you are already doing. You have time to investigate and ponder the path. While I am know you want the situation improved for your child right now, there is time.
