Why did my doc say I tested positive for genital herpes but its not a for sure thing if I have it?

Not sure. What was the test that lead to the diagnosis? If it is a blood test measuring antibodies to HSV 2 and it is positive, it tells you have you got infected and are carrying the virus. You may or may not have had an initial outbreak, though. If you had a lesion that cultured positively, then you have the direct proof you have it.