I havent had my period for at least four months and I was very regular. I have had my period between the last time I had sex and today. Am I pregnant?

Take pregnancy test. Assuming that you've engaged in unprotected sex w/o any use of hormonal birth control, lack of menstrual period raises question of pregnancy. Best way to answer your question isn't online but by taking inexpensive home pregnancy test, available at most pharmacies w/o prescription. They're all accurate as soon as you're late. Then go see Family Doc for either contraception or prenatal care.