First, before assuming anything, your bf should get tested. If you've been having protected sex, the chances of him getting hsv2 from you are quite low - about 2-3% a year.
It's possible that you have oral hsv1, and gave him that from the oral sex, but the timing of that is suspect because the symptoms appeared so soon after. Herpes symptoms appear no sooner than a couple of days after exposure. Was he tested prior to dating you? I ask because if he has hsv1 already, this scenario isn't possible, since his antibodies would protect him from getting it in a different location.
You have antibodies already for hsv2 that would protect you from getting hsv2 orally, and oral hsv2 is rare. Herpes doesn't typically go from the genitals to the mouth.
Your bf can go to an urgent care or walk in clinic and ask that his blisters get a type specific hsv culture, or preferably, a PCR swab, especially if they are a few days old or older. PCR swabs are more sensitive.
I understand that he's processing, which is normal, but you didn't suddenly become a walking biohazard. Be careful that he doesn't make you feel like one now that he has symptoms of something.