You wont feel movement at this stage obviously, but as early pregnancy hormones make the bowels sluggish its possible you're feeling your digestive system bubbling away. Kind of like farts on the inside.
Well, 2-3 weeks is actually the time for other pregnancy symptoms to surface like nausea, cramping, bloating etc. If you just have fluttering that could be purely because of excitement. However, do take a home pregnancy test or a professional test to confirm it at your earliest.