I just started my period 4 days ago and ever since I started I have been constantly lightheaded. A little queasy as well but no other symptoms. My blood pressure was even running 90/57 two days ago but is back to normal...yet the lightheadedness has not let up. This has been a very light period. I have checked sugar and it is fine. I am not dehydrated. And I am pretty sure I am not pregnant. Any idea as to what this could be?