It sounds much like blood-sugar lowering more than anything else.
If you want to be positive about it, do some investigative work
yourself before going to ER or your doctor.
Buy or borrow a BP/ &heart-rate monitor, and Blood-sugar self-measuring unit
, and take some "Normal" readings. THen when an attack comes on, take them again then.
NOW you have something positive to show the doctors. and they have something to go on.