Missed Period..Negative HPT..help?

Hi! I'm 19, and i have had completley regular periods since i was 9. And my last period was march 7, and its now april 11th with no period. im never late. and i have had unprotected about 5-6 times since my last period, and where my guy came in me, no pull out, no birth control, nothing. And i took a winn dixie brand pregnancy test, and it came back negative. Whats the dealio?