Hi..I was just reading about your problem and it sounds like something similar that happened to my mother a couple of months ago. Have you went to the Dr. or the ER yet?
I took my mom to the ER and they couldn't find anything wrong, and sent her home after 6 hours of tests! She has a follow up with her OB today...so I hope they find something.
Anyway, I Would be interested in finding out what your Dr. says.
Good Luck whatever it is