I'm 21 wks & I would say a pretty good description is like butterflies... now I'm starting to feel stronger pushing/kicking but I'm not sure I recognized it this early my 1st time around. I remember towards the end when I would do a "kick count" for my doc I would drink a glass of milk then go lie down & really focus on the movement. If u are go go go all day long then its likely u are feeling the movement, but just so occupied w everything else u might not notice it. Try not to worry too much... we're halfway there! good luck :)
the baby is still very very small. Some people don't feel the baby move til 23-24weeks. Some people think its like butterflies others describe it as popping feeling. If your worried phone your doctor or midwife they will be able to check babies heart beat. Good luck.