This sounds worthwhile doing the testing to eliminate herpes as a cause. It may be due to other factors.
You could go back and check whether your testing included IgG antibodies for HSV1 and HSV2.
Also, does your fiance get oral cold sores? Has he been properly tested for HSV?
I'm afraid the standard STD testing panel does not include HSV - you have to ask for it specifically.
Yes the blisters could be due to other things - a lot of things mimic herpes blisters.
Hopefully you had your symptoms swabbed early enough, before 48 hours had passed, otherwise you risk a false negative.
You might suggest that both you and your fiance go to get tested together for everything, to find out what each of you bring to the relationship. There are lots of critters out there besides HSV!
Congratulations on your impending nuptials!