Hmmm ... ask your primary to request a "tilt test" for you. I was having symptoms that are similar to what you're describing, and was diagnosed as having orthostatic hypotension - low blood pressure triggered by positional change. Mine was related to a side effect of a medication I had started about a month before, but there are many things that will trigger the condition. Also can be related to low sodium condition in the body or adrenal malfunction