When I got my doppler at 14 weeks I could hear her heartbeat right away within a few seconds, loud & clear for as long as I wanted. Now, at 19 weeks it's harder to find & I can only hear it for a few seconds before it's disrupted by loud sounds (I don't know what?) and then I have to look for it again. I thought it'd be easier to find as she's bigger? Anyone else experience this and know why?