What are the possible causes for the fluttering feeling in my stomach?

Many times its heart: Sometimes palpitations from the heart can feel like a stomach problem. The opposite is also true. So a n ekg and or a holter along with a GI work up such as an upper GI may be needed. The stomach and heart share nervous innervation and can have "cross talk". A thorough history and physical should be able to point your doctor in the right direction.