How long ago did you have unprotected sex? If it has been two weeks (at least), you should take a pregnancy test. If you missed a period, you should take a pregnancy test. If you have had your period since the unprotected sex happened, you are not pregnant.
If it has been only a day or no more than 72 hours since you had unprotected sex, you can buy the morning after pill. This pill can prevent you from ovulating (releasing an egg) and it can also prevent a fertilized egg from implanting into your uterus. It will NOT end a pregnancy...it is not the abortion pill.
If you are pregnant, you need to see a doctor asap to make sure you are in good health and that the pregnancy is progressing normally. Your doctor can also talk to you about options available to you regarding pregnancy and parenting.
If you are not pregnant, please always use condoms. And invest in hormonal birth control for yourself. The condoms will protect you from STDs and STIs and will also help in the event that your hormonal birth control should fail...which is rare. Hormonal birth control (shot, pill, patch, etc)will protect you against pregnancy, provided you use it properly. It also has the added benefit of regulating your period and can also help clear up severe acne.