My period is 8 days late, and I've taken two tests that have come back negative, My partner and I didn't use protection, could I still be pregnant?

Unlikely now. Certainly, we all are very eager for accuracy and speed when it comes to the diagnosis of pregnancy. It is unlikely that you are pregnant - given the negative preg. test at this time of your missed cycle. It does take approximately one week after a missed menses to begin to reliably verify a pregnancy by a urine test. Consider retesting in one week. Avoid medications until then. Good Luck!