I had a painic attack once and this sounds like it... panic attacks can increase blood sugars. There is an article on panic attacks on helium.com. Panic attacks can be triggered from something physical or mental... either way, the result is the same.
If this happens again... take sugar test immediately.. If it's under 200... try eating something that will add tryptophan (spelling) like a turkey sandwich or milk. If the attack seems severe and sugars are high... professional help may be needed. This is my opinion only... please talk to your regular doctor about it (not the one in ER since they don't have your history, etc.)
No, there as not really such a thing as withdrawal. However, you don't say how high your blood sugars were either time. If you were high enough the first time to end up in the ER that means you had a lot of stress on your body which can manifest emotionally as well. It takes awhile to recover completely. Very high blood sugars can cause various feelings and symptoms including anxiety (as can lows). Also, as a newly diagnosed person with diabetes it is understandable that you may be having a very anxious reaction to the news. Adjusting to diabetes and learning everything you know can be overwhelming. As some time passes and things get back to normal for you, if you continue with a high level of anxiety you might want to talk to someone.