Unfortunately, I don't have an answer. I am having the same type of problem and searching for an answer. Have you found out anything more?
I've found some other people, including men, who have this problem at http://www.steadyhealth.com/viewtopic.php?t=107145&name=weird_fluttering_sensation_in_upper_left_abdomen_&postdays=0&postorder=asc&start=0
I'm posting this site in my answer because I've found the largest group of people there trying to find a diagnosis. Hopefully, if enough people work together to pass information at a central site, we'll all find a solution. Hope this helps.
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