It's MUCH too early to take a pregnancy test. Only one week after unprotected sex, you wouldn't even BE pregnant yet - not even if an egg had been fertilized then. It's going to take at least 10 days after fertilization before the fertilized egg implants into the lining of the uterus and establishes a pregnancy. Until that happens, you're not pregnant. If you took a test only one week after having sex, the only possible result you could get would be "Negative".
If the only time you had sex was one week ago and your period is now a few days "late", it's highly unlikely that you're pregnant. You would have ovulated (the only time during a month in which you CAN get pregnant) about 2 weeks before you had sex.
One week after you have sex is too late to take the morning-after pill.You have to take that within 72 hours of having sex. At this point, there are no pills you can take in order to avoid pregnancy. If you find out you're pregnant and you don't want to be, you're going to have to have an abortion.