I had sex for the first time last week and now i'm getting red brown spotting. i took a pregnancy test yesterday it can out negative. we used condom?

Probably normal: If you used a condom, then the chance of pregnancy is extremely low. Also, if you had conceived, most tests are reliable for pregnant / not pregnant at about 2 weeks out from conception. So, to be sure about what is going on, take a test two weeks from intercourse and consider getting on birth control pills as well!

Hymen: Possibly this is still some retained blood coming out as the red/brown spotting from your hymen being broken during your first sexual encounter. If it persists, see a gyn now that you are sexually active, and birth control can be discussed as well. Best wishes.