My first question would be; how are your blood sugar levels? I have low blood sugar and if I have not been eating enough I can get terribly dizzy/light headed/faint... my heart rate also goes up... it is most unpleasant and can be frightening. As disturbing as it can be though, it is a simple enough fix... try eating something like a few pieces of toast or drinking some juice and see if things get better. I hope it is something that simple and that you are feeling better soon.
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"...don't ask me why it's just the nature of my groove..."