I haven't had my period now for 18 days and i took a pregnancy test and it said negative am i pregnant or not?

Preg test: The pregnancy tests are very sensitive, so most likely,..NOT. You may have had an anovulatory cycle, so wait to see if your next cycle produces a period. You can always obtain a serum pregnancy test if you are too nervous to wait until the next period would arrive. Best wishes.

Not pregnant: if test is negative. If you miss your next period and a pregnancy test is negative see your GYN.