It may be sensible to discontinue the medication for a while and see if his anxiety diminishes. Talk it over with the prescribing doctor. If he stays on medication, Adderall XR may be a suitable choice for his age.
It did start after the medication, but quite a time after. He has always had some small fears such as monsters under his bed and things like that, but nothing this severe. He started on Focalin, but it wore off too soon. So the pediatrician put him on the Vyvance. He is more hyperactive than attention deficit. His hyperactivity is off the charts.
It's unlikely the behavior is a side effect of the medication. Did the behavior have its onset after he started on the medication? His behavior typifies separation anxiety, and he should be in treatment for this. Treatment can include both medication and therapy (including parent guidance). It's interesting that he is on Vyvance - that's not typically prescribed for a child so young. Was there a particular reason for choosing it?