How do i know when my maltese is going to give birth?

She is discharging a yellow liquid of some sort. today is her due date and she is shivering when i talk nice to her. i know i should have but i didn't/don't want to shove a thermometer up her. and i do have a whelping box ready for her. She never had the nesting stage but does stay away from our two other dogs and is pretty aggressive towards them. any help? and PLEASE NO MEAN COMMENTS. i just want some help