Have you been so to see someone to have these blisters cultured? Are they gone now? The blisters could have been caused by either HSV 1 or HSV 2. When you say that you had oral sex, does that mean that you gave or received oral sex? If you received oral sex from your partners, even if they didn't have a cold sore, they could have been shedding virus from their mouth. Unfortunately, STD screening doesn't always (or often) including testing for herpes, so hard to say what it means that they tested negative for STDs. The blisters could be other things, yes, but the key is, did you get tested?
Terri
Terri
Terri