Is it true that a positive opk test can mean that you're pregnant?

Ovulation prediction: I assume you're referring to ovulation prediction kit (opk). If that's the case, a positive test confirms you've ovulated but says nothing about pregnancy. To determine if you're pregnant, you need to take a pregnancy test (not ovulation prediction test). Of course you need to take test as directed, in other words, at least 4 wks after last menstrual period, not just any random day less than 4wk.