I have the same problem, especially during that TOM. I think it is related to low blood pressure, which I have also. I actually faint during TOM when I stand up to fast. I think it is related to diet, in a way. You know, diet affects fluid levels, sodium/potassium intake, etc.
Here is a website to check out, evidently, it can be a serious problem:

http://www.naspe-patients.org/patie...ting/index.html

"Some types of syncope are preceded by warning signs (presyncope) such as dizziness, nausea, stomachache, chest pain shortness of breath, or sweating. By learning to recognize the warning signs and lying down with the feet elevated, some people may be able to avoid a fainting episode. If you are susceptible to the common faint, you can take precautionary measures such as:

Drink plenty of water and other liquids
Avoid dehydration and overheating
Do not restrict salt in the diet
Wear compression stockings or other snug clothing, such as stretch leotards, on the lower body
Talk to your physician about any medications you are taking and ask if they might contribute to fainting."

You might not be fainting yet, but it sounds like you have the warning signs. I personally have never cut back on salt in my diet, because it happens more frequently when my BP is low.

Let me know if anything helps, and I will give it a try, too!

Disclaimer: I'm not a doctor, consult a physician if symptoms persist, yada yada....