I m 43, 113lbs, 5 2 and live a very stressful life but generally healthy. About a month ago I had a flutter that was constant and rhythmic but not painful under my left breast that lasted about a week. Now, for 3 days I have had the exact flutter (like a purr) at the lower part of my back, internally, right where the crack of my rear starts. It flutters every 4 seconds when lying still and if I exert myself its constant every 2 seconds exactly until I lie still for a few moments and then returns to every 4 seconds.