Still late

Last month I started my period on the 15th glow said my period would be the 12th I didn't start so it then moved my period to the 15th, still haven't started now it says I'm due tomorrow. I'm having mild cramping on my right ovary but not actually cramping like I usually have when I start I've taken 4 test from the 12th of this month till this morning all are negative:/ I went for blood work on Friday but I'm afraid it will be negative and don't want to be let down. P.s usually never just miss a period unless I'm pregnant.