your body has to have had time to produce detectable antibodies that the tests react to. I think it's still an excellent idea to get a good blood test so as to establish a base-line. Ask for the HerpeSelect IgG for both types 1&2. Some people produce IgG antibodies as soon as 3 weeks, but others take as long as 3 or 4 months. What this means is that if a test at 3 weeks produces a positive result, it can be trusted, but a negative can't. By 16 weeks, over 98% of infected folks will have a detectable antibody response. If that's not clear, let me know and I'll try again.
I'm with you that I think it could just have been some sort of irritation. When we're worried about herpes, we often assume the worst.