Just popping on real quick to update y'all on my doctor's visit this a.m. She said the fainting is most likely because I have low blood pressure -- but she says it's not dangerously low. She suggested I drink much more water, eat salty snacks such as almonds and pretzels and to lay down immediately if I feel dizzy. She also told me to check my BP every time I go grocery shopping, just to keep an eye on it, but not to worry too much.
Thanks for everyone's thoughts yesterday!