I am sorry to hear your 13year old is getting bullyed. That must be really frustrating. I only have younger kids, so I imagine myself in your shoes and it seems like it would be really difficult to not be able to stand up for your child.
I did some research.
If you are looking for supplements to help with anxiety, you many want to checkout 5 htp for anxiety.
Also be aware that a side effect of concerta is anxiety: http://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=33085
You may want to just try not using the concerta or replacing it with a product that uses natural supplements for ADHD.