This could be a sign of hypoglycemia.
Test yourself with the

The Nutrition-Behavior Inventory Questionnaire (NBI) at:
http://www.hypoglycemia.asn.au/artic...inventory.html

and the

The Hypo Quizz at:
http://www.hypoglycemia.org/hypo_test.asp

If you score high go on a hypoglycemic diet