D.,
Let's start with the weight loss. This is due to the fact that meds for ADHD are actually amphetamines (uppers). In everybody for all amphetamines they cause you to loose your appetite (that's why they are the first ingredient in most OTC diet pills). Secondly, I want to know who diagnosed your son, a PCP, a teacher or a psychiatrist. ADHD sympotms can mimic other issues, aka food allergies, metabolic disorders, etc.
My first suggestion would be to see an allergist to rule out all food allergies. If this comes up negative, I would request a fasting blood test to rule out other basic metabolic disorders.
I worked with true ADHD kids for years, and have been watching the instances of ADHD diagnoses rise over the years. I think that many of the diagnoses are inaccurate but because ADHD is one of the more popular and better known diagnosis, it causes children to get pigeon holed into this diagnosis.
Okay if the blood test comes up negative, I would request a sleep study. Believe it or not there are many studies that indicate that ADHD behviors are because of sleep deprivation. I don't mean he doesn't go to bed early enough, what I mean is that these children are either snoring or suffering from sleep apnea and are waking themselves up frequently during the night making them overly tired. Think about it, how do you act when you are tired. Irratable, irrational, many of the symptoms that ADHD children exhibit. Also, you add the amphatime meds (which would be like you adding coffee) you get the exact symptomology. An easy test for you would be to listen to your son sleep. If he is snoring, this may be the case. Many people think that snoring in kids is normal. It is not. It may be symnptomatic of other things like asthma, or enlarged adnoids (the glands next to the tonsils). If he is snoring, I would suggest looking into asthma, airborne allergies, or the enlarged adnoids. If you get this health problem corrected (aka antihistamines for allegies (or even an air filter), get the astma under control, or get the adnoids/tonsils removed) the child stops snoring and thus waking himself up, and guess what, the symptoms disappear like magic.
If you need the studies, e-back and I will find and forward the studies to you to talk with your doctor about. I don't blame you for feeling guilty about the meds, but I do suggest that you rule EVERYTHING else out that could be causing the issues before getting a firm diagnosis of ADHD (what you are calling ADD, and the fact that your doctor called it ADD instead of ADHD scares me because very few doctors call it ADD anymore. ADHD is the official diagnosis now).
Good luck, and if you need to talk, e-back.
L.