You need a full evaluation. Take him to a board certified child psychiatrist and a Neruopsycholgist. Do both. Once you get the evaluation data on his educational and processing skills, you will have a better idea of what is going on here, and you can actually get a good diagnosis. Try treatment with the psychiatrist, one medication try is not adequate, that is, if ADHD is the diagnosis, or if he has a diagnosis that requires medication. Medication is a tool that will help him manage symptoms so that the other therapy he needs for education and social-emotional-behavioral skills can be more effective. Your cart is way ahead of your horse, get him evaluated ASAP, you really need that Nuropsychological evaluation data and a psychiatrist to use that data to confirm a diagnosis and help you plan a multi facited, sustained treatment plan.
You especially need to have his memory processes assessed. This could be consistent with ADHD, if he has retreival issues related to attention. You just don't know with out the data. Go get it as soon as you can.
The school should be doing evaluation of their own, a child who cannot count sequentially by age 10 will have educational needs that should have already drawn the attention of his teachers. Is he on an IEP?
M.
Edit: At least 25% of children with ADHD are dyslexic also. Evaluation is essential, you don't know what your son has if you have only been to a neurologist and only tried medication. There are many different conditions that cause simular issues, and it may not be just as simple as a diagnoses followed by treament followed by recovery. It is much more complicated than a diagnostic "word". Please get the evaluation so that you know what the educational needs are, like processing speed, and working memory, visual processing and information retreival skills-I suspect that these are going to be important factors in how you remediate what ever this is. You need him to have a Woodcock Cognative (a neuropsychologist will know what this is.)