Tested 3 times for pregnancy all bfn. 12 days late. noticed dark veins all over chest today. major lower back pain. could i still be pregnant?

Tests are accurate: Pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, vaginal spotting or medications. A 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 negative result may be due to testing too early such as less than 2 weeks after conception.