is it a movement or am I just crazy?

So I have been feeling the odd twitch/fluttering in my belly and I don't know if it's just a muscle spasm or if it's baby moving? I don't really think I am showing to much. It's not completely obvious that I am prego although wearing my black sweater sure makes my belly look rounder :( I used to feel skinny when I wore that sweater! LOL not anymore :(