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!
Use first morning urine and try a pink dye test like first response early for an accurate result. Good luck.
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.