Yes, a negative IgG is pretty reliable, depending on the timing and the type of herpes. THe hsv2 IgG misses about 8% of infections, and the hsv1 IgG misses about 30%.
The IgM is worthless, and even if it worked as designed, it would only detect a new infections, so it's worthless for you, as you'd have an established infection.
The swelling makes it sound more allergic than herpetic, though obviously, I can't make that determination for you officially.
Did your doctor just look at it? A visual diagnosis is wrong as often as it is right, so I wouldn't put a lot of stock into that. If this happens again, get to a doctor within 24-48 hours of the blisters appearing, and ask them to do a type specific culture on the blisters so you can put this to rest.
Even with the testing flaws, since you had used corticoid ointment, and recently had this with swelling, it doesn't sound like herpes to me. The only way to know for sure is to get the blisters cultured and typed.