Hi,
Several factors can cause your period to be late, such as: stress, an irregular period, change in medications, illness, change in diet, miscalculating your next period, etc... Because you mentioned unprotected sex, naturally you must consider the risk of becoming pregnant. Even if you believe that he didn't ejaculate during unprotected sex, you should still take a pregnancy test. I suggest taking a test because it will help you more accurately determine whether you're pregnant, or not ~ it can also help put your mind at ease.
Take Care