Is your child getting any help for the sensory issues. Untreated those can cause anxiety symptoms. I would see a child psychiatrist if you have not yet done so. I would contact the prescribing doctor and tell him/her the symptoms your child is having, they might fade over time.
It is possible that your son has both ADHD and anxiety issues. However, it is common today for medical personnel to misdiagnose a child because the behaviours for some anxiety disorders and ADD/ADHD are very similar. Since the medication for ADHD is not working, I wonder if this could be the problem in your son's situation - he suffers from anxiety but not ADD/ADHD.
Usually, the medication for anxiety is one of the SSRI's - non-habit-forming medications. Some examples are Celexa, Zoloft, Prozac, etc. By the way, sensory issues and/or depression tend to be very common with children suffering from anxiety. What do I feel you should do now? - I think it might be wise to speak to your son's doctor and express your concerns. If you feel that he/she is not able to help you, then request a referral to a pediatric mental health specialist (as a child neurologist or child psychiatrist) for more prudent advice. I wish you the best ...