Baby kicking - when?

I’m also at 18w and I can’t really confirm if I am really feeling baby movements. What I feel are random and weak swishes/vibrations/squirms that feel abit like a small fish swimming against a bag. But I can’t be sure if I’m imagining it as I’m have no prior experience. Friends say theirs are like bubbles or flutters. Appreciate if fellow mums can share too!