I've been diagnosed for 7 years now with what they call iron overload disorder (haemochromatosis) to make a long story short it messes with your MCV, RBC's and ferretin levels. E.Q. has a great effect on red blood cells as well. Anyway, the change in blood volume, MCV, RBC, iron saturation and hemoglobin can give you a similar "fluttering" tight or anxious feeling. When you combine alcohol (if you guys drink) into the equation it makes things much worse. Do you notice it get's worse if you drink or if you drink while on EQ.
Maybe think about getting your ferretin levels cheked some time to make sure you don't have this disease / disorder.