Are light periods a sign of pregnancy? blood stays inside vagina. happening last 3 months. got 10 negative hpt and blood test

Tests are accurate: 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 correctly, a negative test result means not pregnant regardless of vaginal spotting or "light periods".