The only thing I can tell you is that I've been there! I've felt the same way! You can go to the ER just to reassure yourself if you want. Do you have a blood pressure monitor? If your blood pressure is low, you may need some salt. If your blood Sugar is low - eat something! I don't typically advocate Gatorade but if you feel like you are absolutely dying... drink a glass of Gatorade and see if that helps your electrolytes before you go to the hospital.
I can't tell you that you aren't having some type of major health crisis where you should be at the hospital but I can tell you that I felt the same way during the beginning of NB. Like I've said before - the hypoglycemia, dizziness/fatigue, low blood pressure, and RIDICULOUS anxiety/paranoia (especially about my health) - it was unlike anything I could have ever imagined.