Do you track your ovulation or are you late based on when your period usually comes? If you're late based on your ovulation date I would call your doctor for a test if you don't get your period in a few days. If you don't track ovulation it could just be that you ovulated late this month. If that's the case I'd give it maybe a week to see what happens.
Use first morning urine and try a pink dye test like first response early for an accurate result. Good luck.
You could have ovulated late, therefore your period isn't due yet, or you're not getting a positive yet, so wait another week if no period by then, and take another test. If it's negative make an appt. with your OB/GYN and get a check up as to why your period is late! Good luck!