Your son sounds quite a bit like mine. The medication road for us has been a long haul.
difficult child diagnosis'd with-ADHD at age 4. By this point we had to try something as difficult child already had been through 2 daycares and husband and I worked. Tried Metadate (stimulant). Horrible rages, destroyed preschool class room. Same psychologist said oh well he must be bipolar since he reacted so badly to the stimulant. Put difficult child on Risperdal to help with the rage/aggression. difficult child ended up having a physical side effect to that medication to we took him off of it and changed to a psychiatrist.
First psychiatrist said he's just ADHD. Placed him on Ritalin. Never worked for him. She wouldn't listen to us that more was going on, just kept throwing prescriptions for stims at us. We dropped her.
Next psychiatrist said he was bipolar and ADHD (bipolar history on husband's side, mother & aunt, but not husband). We trialed Lithium (didn't help), Depakote (stayed on for a while) added Abilify (could never go past 5 mg with-difficult child or he was get nasty). Once semi stable Dr. tried to get a handle on the ADHD. Adderrall, Vyvanse, Daytrana, Straterra and Tenex comb, guafacine, Dexedrine, Focalin you name it, we trialed it over a 2 year period. Every stimulant aggitated this kid.
We did a medication wash under dr supervision, but towards the end difficult child became unstable and spent 3 weeks in a child psychiatric unit at a major ivy league hospital. They put him on Seroquel for mood) and Nortriptyline (a second generation anti-depressant), he did well for a small time, but I noticed itching and tics with it, and drooling. We got him off of Nortrptyline and it all stopped.
After the psychiatric hospital stay we rallied and got in home services 2 times a week (n/c) and signed on with their psychiatrist as it was a lot closer and they took co-pays vs a long drive and cash straight out of pocket. That dr saw anxiety and added prozac. He has been on Seroquel and prozac for just over a year and is doing so much better. The prozac really opened him up to learning in school.
I must also say that we've been at this for over 3 1/2 years with difficult child and he is only 7. His first neuropsychologist was at age 4. In first grade we made the decision to move him to a therapeutic school in 1st grade that our school district pays for. He recently had a second neuropsychologist this past summer as part of a consortium researching autism (we were thinking Asperger's, but it's not) and thorough testing from the SD last spring (they specifically brought in an expert and did not use their school pysch for testing).
I really think the therapeutic supports (in our case) were key and the school setting has made a difference. Once he got there and settled in and with the addition of prozac at that time he began to learn his reading exploded and he is currently in 2 grade and functioning on a 4th grade level in math. They have just started to mainstream him (as his program is housed in a wing of a huge mainstream school) and it's going well enough that they are getting ready to add another mainstream class for him.
The medication road is a HARD one as many here will atest to. Depending on what you are dealing with there is no quick fix for a lot of what our kids are dealing with. I hope too, like Smallworld said that you are able to get a working diagnosis before just jumping in to medications because things could get worse but whatever you decide good luck to you. Know that there are others out here.