My period date has always been around the 24th of each month then in december i skipped and it only started on the 14th of january it is now the 17th of february and i still have not has my period? did 4 pregnancy test all negative

Tests are accurate: Home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, or medications. A correctly done urine test gives a reliable result 3 weeks after sex (3 weeks after when conception might have happened) 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.