If a woman doesn't have her scheduled period does that mean shes pregnant?

Maybe. There are a number of reasons to miss a period. In a sexually active, reproductive age woman, pregnancy is simply one of the most common. As menopause nears, missed periods become more common. They are also common when a girl first starts having periods. Also, stress can cause missed periods.
Possibly. Pregnancy is one common cause for a missed period, but there are many others. A pregnancy test is the surest way to find out.