I have been having huge issues with this. I will feel very faint in the shower at least once a week. I will have it throughout the day. I drink water and eat a granola bar before getting in the shower on my work days. On my days off I will eat and drink quite a bit before I get in the shower, and it seems to still happen. The Dr. said that it was low blood sugar and it takes 45 minutes after you eat to regulate, but even if I wait an hour, I still feel faint. I am getting really frustrated with this. It has been happening since about week 6. Is there anything else that can cause it?!
Is it possible it's the heat of the shower and standing for too long? I did research on other sites etc. and I kept reading over and over again that pregnant women would faint when standing in line for too long and were feeling hot. That is exactly how I felt this morning when it happened to me, I got very hot and stood up too fast.
It doesn't sound very appealing, but maybe don't take such long hot showers, if that is what you tend to do (which is what every normal human does).
Also, my doctor told me to eat more protein and less sugar to get rid of the fainty feelings.