Do i have HSV-2 ()?

ok so i got a BJ from this girl and she had no sores on her lips or any thing she looked clean. I have known her for a long time and i was the first guy she has given a BJ to. After 4 weeks i got blisters on my . but 1 day before i got the blisters i masturbated with shampoo and did not shower after. What gave me the blisters. I talked to the girl after and she said it cant be because i was her first to give a BJ to. please some one help me out here.