Welcome to the forum. I'll try to help.
First, though, a plea to all forum users: It is unnecessary to "confess" on this forum. I don't care whether or not you view your actions as a "huge mistake". I don't moralize about behaviors and you shouldn't either. As in the old Dragnet series, "Just the facts, ma'am".
You describe a pretty low risk sexual encounter. If your partner was a professional colleague, the odds are her chance of having an STD before you got together were as low as your own. The transient urinary burning might or might not have been significant -- but if you're not even sure whether it was real or only "in your head", most likely it didn't mean anything. In any case, the antibiotics you received would have cured or prevented any possible bacterial STD: chlamydia, gonorrhea, nongonococcal urethrits (NGU), syphilis. Since you took them before you had sex with your wife, you could not have transmitted any of those infections to her. And there is no point in your being tested for them.
As for your wife's symptoms, it's hard to comment on a second hand report. Herpes is always a consideration for a pimple-like labial lesion. Or it might have just been a pimple. You're not going to like hearing this, but she should be examined and evaluated for herpes. If she has it, it doesn't necessarily have anything to do with your extramarital encounter.
To the specific questions:
1) Gonorrhea is not a realistic issue. Almost all cases cause overt and obvious symptoms that you would not have missed (pus dripping from the penis); and the combination of antibiotics you had would have cured it.
2) As I said above, there is little point in testing now; and even if you had been infected, little or no chance you could have transmitted them to your wife, once you took the antibiotics.
3) Yes. Azithromycin would have eradicated incubating syphilis.
Bottom lines: It is unlikely you were infected with anything; the treatments would have eradicated any infection you were likely to get, and thereby protected your wife; and most likely her labial lesion isn't related to your sexual indiscretion. However, to be maximally certain about your wife's health, she should see her health care provider for evaluation of the labial sore.
I hope this helps. Best wishes-- HHH, MD
Well, your wife's herpes history probably explains the labial lesion. So that's probably even less a concern than I thought.
Also forgot to mention, I don't know if the girl I cheated with has any STD's. She said "not that I know of.." but who knows..
Forgot to mention -- my wife already has herpes which is why I'm not worried about that particular STD..