about babies cries

I have a 7weeks old baby . Other than "eh" "neh" "owh" "eairh" "heh" How else can i know why my baby is crying? & how to console a overtired baby? I cant seem to deciphire what she wants everytime , bcuz sometimes she says "eh" but she wants to drink . My baby girl also cries alot & refuses the nipples sometimes , i even burped her & changed her nappy. Maybe she has a tummy ache or gas but i tried doing bicycle motions & nothing helped. Some help!