How come some doctors say spotting can be a sign of pregnancy and some say it's not? i'm confused

No problem: You may simply have misunderstood what you heard. There no question that spotting is likely a very good indicator of variance in the normal hormonal cycle. Early pregnancy is one hormonal change that MAY produce spotting, but not necessarily. Any other cause of hormonal variation can also result in spotting, so by itself, it's not very diagnostic.