so you had unprotected sex 2 weeks before your period, i assume you're trying to get pregnant then, right? are you ttc?
you could be having a missed period because of stress, or a change in your diet.
i'd say to wait for a few more weeks and if your period still doesn't show up then go back to the doctor and try to find out why, you could be pregnant and just not producing enough hcg to get a positive test, but you never know. like i said, wait a little while longer and if it doesn't show up, then go to the doctor. don't worry yourself, this stuff happens.