We recognized our 11 yo DS had anxiety when he was @4. At different times, it has increased to the point where it was life-impacting. We've seen psychologists, psychiatrists, OTs and partiicpated in anxiety research at NIH. He's learned all sorts of tools and techniques to help him control it but, at times, it controls him. It's really hard for younger kids to utilize learned strategies when they're in the midst of it. In third grade, DS had a really poor fit with a general ed teacher and his anxiety spiraled out of control. That's when we turned to medication (Prozac). He was on it for about 9 months, was able to get his anxiety back into control and hasn't needed it since.
Having been through all this, I would encourage you not just to look for a counselor for your DS but also someone who can help you learn to help him. It can be a fine line between supporting your DS as he works through this challenge and enabling/reinforcing his anxiety. I would suggest you contact the Ross Center
http://www.rosscenterdc.com/services/child-and-adolescent-treatment-program/ for assistance. They have some fabulous providers. I also heard they opened a new center in Alexandria but couldn't find anything about it (I could be wrong). Good luck!