My period is 2 weeks late, did a few pregnancy tests and they came negative.i also have a slight back pain, and sore breasts + nauseous. help please?

Can re-test in 1week: Home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, vaginal spotting, or medications. A test is very accurate by 3 weeks after sex (3 weeks after when conception might have been) 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.