No, you are not pregnant, understanding you experienced a normal cycle when your period did come. Your missed period could have been caused by a number of things, such as, increase in physical activity, or stress. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Your thinking about being pregnant most likely tricked your body. A woman's body can produce some of the signs of pregnancy from the desire/ worrying about a pregnancy. The woman's brain then misinterprets those signs as pregnancy, and triggers the release of hormones (such as estrogen and prolactin) that lead to actual pregnancy symptoms. Men can experience "false pregnancy" as well, it isn't well researched as to why but he may have also had the fear you were pregnant as well and caused what is known as, couvade, or sympathetic pregnancy. They will develop many of the same symptoms as their pregnant partners -- including weight gain, nausea, and backache.
Regardless, in your future when you become more sexually active take the steps to preventing pregnancy. Talk to your mother about being on birth control and have your boy friend wear a condom. There are options such as Plan B for times when you feel your steps of birth control have let you down. Plan B is NOT an abortion pill, it prevents pregnancy if taken within the first 3days after intercourse. The week before your period is when you are ovulating, which means that is the time you are most likely to get pregnant. You should track when this week is as you become more sexually active in your life. But of course, you are worth the wait and no man should ever pressure you into having sex.