Alah tu most likely baby movements dah! 18 weeks is still early so sometimes it feels macam butterflies atau that electric shock feeling you described, some of us describe it like gas bubbles bergerak, others say like angin or light tapping, quite random at first hehe. Don't worry lah, in a few weeks it'll become clearer and you'll feel proper kicks, then you'll be like "oh THIS is baby!" Lepas tu memang tak boleh tak perasan lagi because baby will remind you regularly! Congrats on your first baby, exciting time ni!