AF due the 17th..

anybody know what kind of cm you're supposed to have before flo shows up? earlier today i had very watery white discharge, now i have this. its still white but it thickened up and is kinda similar to egg whites. I have no symptoms of flo showing up, other than my breasts feel very full and tender to the touch and i feel bloated/constipated. I know those can also be pms symptoms but my usual telltale sign is a migraine. I dont remember seeing cm like this before my period for past cycles. any info is appreciated.