I'll try to help. The bottom lines are that the timing certainly is consistent with HSV-1 acquired by cunnilingus with your husband 5 days earlier. There is no way to know how long he has been infected.
You indeed describe classical symptoms of primary genital herpes; given the agreement of both the ER doc and your gynecologist, I think you can be certain about the diagnosis. It is important to know whether it is due to HSV-1 or -2, and I hope the ER tested your genital lesions for the virus; if that was done, the virus can be typed. If it wasn't done, you will have to rely on blood testing to sort it out, which likely will take a few weeks. You should have both an immediate blood test for HSV-1 and HSV-2 and a follow-up test in a few weeks, to see whether the result converts from negative to positive for either virus type. But I hope viral culture or PCR was done for earlier and more accurate typing results.
Whatever type it is, you caught it within 2-3 weeks -- probably 3-10 days -- before your symptoms started. Symptoms can be delayed for months or years, but then the outbreak behaves like a recurrence -- i.e., few lesions, mininal pain, no lymph node inflammation, etc. Therefore, your husband is far more likely the source than the extramarital exposure 5 months ago. It could be either type, but HSV-1 is much more likely than HSV-2 if you and he haven't had genital intercourse recently. From the information provided, it isn't possible to judge when your husband was been infected, and nothing to imply he has had other partners recently.
The good news is that since your husband is the probable source, you need not take any precautions in the future to protect him from your infection. Once infected with HSV-1 or 2, people are immune (or at least highly resistant) to re-infection with the same type. For this reason, couples do not "ping pong" their mutual HSV infections back and forth..
I recommend your husband be evaluated, including blood testing, which will tell whether he is infected with HSV-1, HSV-2, or both. In the meantime, I see no need to reveal your extramarital exposure 5 months ago, which is not likely to be the source of your infection,.
Closing judgment: Most likely this will turn out to be HSV-1, probably acquired by the oral sex event with your husband. If so, you can expect to have few or no recurrent outbreaks, when tend to be much less frequent with genital HSV-1 than HSV-2.
I hope this helps. Best wishes-- HHH, MD
I meant to say that even though the ER didn't necessarily order virus typing, they might have at least done a culture or PCR test to identify the virus. I hope so. If that was done, then the lab can be contacted and asked to type the virus if the initial test is positive.