Will pregnancy test be accurate 17 days after sex? i dont have a normal period bc i am on nexaplanon so if its negative 17 days after sex is that accurate?

Better at 21 days: Today's home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, or medications. A home urine test will give a reliable result by 3 weeks after sex (3 weeks after when conception might have been) or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon.