If you are having 28-30 day cycles, you were in the safe period and you need not worry about getting pregnant. Since ovulation usually occurs around 14th-16thday in such cycles, fertile period when intercourse can result in a pregnancy
ranges from 11th-18th day. Beyond that chances of pregnancy are very little. Remember, ovulation almost always occurs 14 days before next cycle. You can have an examination from your doctor if you miss your period, which is most unlikely. Take care.