The giver of oral sex can contract herpes if the receiver has herpes. The name genital herpes is to location. So if you have HSV1 (oral form of herpes ) and perform oral sex on someone who doesn't have have herpes it is possible to pass Herpes to the receiver. This is also true for HSV 2 which is more connected to genital herpes. When you hear people say genital or oral herpes we are talking about location
Testing centers reccommend the window period of 12 - 16 weeks because many people develop enough detectable antibodies in that time frame. You can get a test before that but I would retest within the window period.
When you do test, I would suggest the Herpes Select Test. This ia specific typing blood test that can be performed if no active lesions are present.
Hopefully betseyb1967 will respond. She has awesome info and can give you great information ( Major Props Ms. B)