Thank you for your question and welcome to Empowher. I will assume you missed a period and thats why you are asking this question. Pregnancy tests are usually 99% accurate and if you took two tests and both were negative, you should be fine. You can always make an appointment with your doctor for a blood test, but seems to be pretty safe to say that you are not pregnant. You should usually wait at least 1 week after missing your period to take a pregnancy test.
I hope this helps and keep us posted.