How Soon Can I Take A Pregnancy Test Inspite Of Having Late Periods?

Hi i am just enquiring i have got nexaplan out on the 27th of january and had unprotected sex the night before removal. I was ment to take my period on the 4th of february and still no sign of it. I have been feeling nausea and light headed and have bee having pressure on lower stomach and lower back. I have also had perriod like symptons. I have took 2 pregnacy tests but both negative. Would just like some advise thanks