Does a positive ovulation test mean I'm pregnant?

No. The ovulation test looks like a pregnancy test, but they measure different things in the urine. The ovulation test measures the hormonal increase (lh surge) that leads to ovulation. A positive test means that you will likely ovulate in the next 24 hours. The pregnancy test usually measures a specific hormone secreted by the developing pregnancy (beta-hcg), so a positive test indicates pregnancy.
No. It probably means you ovulated. Opk is a very poor test for pregnancy; it is less sensitive and more $$ than a home pregnancy test.