No your probably not pregnant but you could be premenstrual which is why you have breast/nipple tenderness. But......
If you don't get your period as expected, do another test. However there are other reasons for not getting a period.
its not likely for you to have been ovulating. and you got your period. chances are your not pregnant....but your on your road to becoming pregnant soon.
anytime you have unprotected sex you can be come pregnant. especially if a guy is ejaculating inside of you.
use birth control as well as start using condoms