First off, he is in preschool...his teachers KNOW nothing about his status as far as a learning disalbity, unless they sent him to have a full, multifactored evaluation, and even if they had, he is in preschool, so you still don't know.
What they should have told you is that this is a smart boy. They should have told you that he has attention issues and that he has trouble following directions. They should have told you WHAT they see, not what they THOUGHT about what they see. Sorry, had to get that out, it is just infuriating that teachers, let alone preschool teachers, make diagnostic suggestions to any parent.
They had every reason to tell you that you should consider getting an evaluation. You need an evaluation, and this is not something that you can or should get from your pediatrician. You need a Developmental Pediatrician. You need a full developmental evaluation, one that will inlcude his intelectual processess, his academic acheivement, his motor skills, his sequencing skills, his speech and langague processing skills...and anything else that may be relevant to your son. Let the Developmental Pediatrician tell you what, if anything, he may be diagnososed with. Maybe it is not ADHD? You have a reason to have a Developmental evaluation, getting an 'ADHD" evaluation is illadvised. Let me put it this way, you do not go to the doctor to see if you have cancer, you go because you have a pain here, or a twinge there, or a symptom...you tell them what bothers you, and they ask you questions, send you to a specialist if you need it, and they run tests and they tell you what is wrong. As CAWriter said too, you can use a Neuropsychologist and a psychiatrist as well, but you may need to add in things like OT and speech.
There is no evidence that the natural supplements or diets work. Unless your doctor suspects an allegy to a particular food, you should not be chasing this because it will not be helpful, and is only first line treatment for those with an identified allergy.
Remember this: Brain disorders (like ADHD) are not DIY pojects. They are seriousl business, and you not only need a full evaluation to idenify what, if anything, is going on, but you need an expert to help you develop a treatment plan that is appropriate for your son, based on his data and medical needs.
If this is a PUBLIC preschool, your teachers have just obligated the local school district to also conduct a public evaluation of your son for ADHD, and you can request that it include more than just ADHD if you suspect it. You need both public and private evaluations. If this is a private preschool, go to your local school district and tell them that you suspect that your son has a disablity, and ask them to evaluate him. Again, you need both public and private. You should never know less than a school district about your son, or what he needs. The school may be obligated to provide services to your son such that he is functional in the school enviornment. You should negotiate for as much as you can, then provide the rest privately so that he can reach his full potential.
Good sources of information are for ADHD are CHADD, www.wrightslaw.com, additudes magazine, and any book by Dr. Mel Levine or Dr. Russel Barkely. If it is something other than ADHD www.wrightslaw.com is your bible for learning to navigate schools.
Good luck. Get a full evaluation from someone other than your pediatrician. If your son needs medication, it should come from a doctor and a pharmacy, not the internet or the supplement isle in the whole foods store. If he needs medication, it should be used to make all his theraputic services more accessable. Medication is a tool, it should be accompanied by many hours per week of play therapy, cognative behavioral therapy, social skills classes, speech, OT, vision theapy and developmental optomitry services, and extensive behavioral supports at home, and school and educational accomodations.
M.