Pregnancy still a possibility?

Recently had unprotected sex, he did not pull out, supposibly startied ovulating maybe 3 days later, 1 week after sex had a red/brown spot in underwear, period of was 2 days late, took a test, came up negative. My period is extremely light and barely shows up on a pantie liner. Its more of a brown color and sometimes a very light pink. Is pregnancy a ruled out solution or is there still a chance I am? Thank you. Answers are appreciated