What else would feel just like fetal movement other than gas?

I am 18 weeks pregnant and feel my baby on again off again. Mine feels like popcorn popping inside or like something flicking the inside of your lower abdomen right below you belly button. But it feels different to every woman. Some say it feels like when your on a roller coaster and it does that belly flop thing. Or like a butterfly flapping its wings flying inside of you. Whatever it feels like to you, you will start to know more and more as you feel it more and more...good luck!