Had unprotected sex the day i started my 2nd bc pack. feeling nausea recently. am i pregnant? how accurate is the pregnancy test (2 weeks since then)?

Very accurate : Pregnancy tests, even over-the-counter ones, are very accurate. Generally, if you conceived more than 14 days ago, the pregnancy test will be positive. There is a small chance that the sperm lived inside you for a few days, and you conceived too recently for the test to pick up the low levels of hormone in your system. You can repeat the test in a week to be safe, but this is very unlikely.