The only way to know if it is a recent infection is if you test negative for HSV-2 IgG antibodies at this point in time. This would be a typical IgG type specific HSV test. However, if you already test positive for antibodies, the doctor cannot tell you how long you've had it for, unfortunately. Sometimes they would try to tell you based on an IgM test but if you've read the other forum or done your own research, you'll find that those tests are not accurate enough to be reliable.
If your infection is less than 3 weeks old or so, you'll probably be negative for antibodies. Beyond that, the odds of being negative go down as time goes on. So since you're probably around 4 weeks into it based on your post, if it's a new infection there's about a 50% chance you'd still test negative.
With HSV-2, I'm going to say it's more likely the infection is a new one. Your partner probably has an asymptomatic infection, which is pretty common. Especially if he picked it up earlier in life and hasn't had an outbreak in decades.
The easiest way to find out is to have your new partner tested.
I understand what you are going through because I recently discovered I have Herpes and when I looked back at previous test results to get a time frame of how long I've had it I discovered that as far as I can tell I've never even been tested. Here I was every year going to the obgyn telling them to test me for "everything" and trusting that was what they were doing. Well "everything" doesn't include Herpes unless there are visible signs of an outbreak or you specifically ask. Now I have planned to go in there with a list of what I need to be tested for, and I will verify the results with the list just to make sure they really test for everything.
I'm pissed too but unless you can tell for certain that you didn't have it before there really isn't an answer. I think the doc can tell you if you've gotten it within the last 3 months or if you've had it over 6 months, but again you have to ask because they aren't helpful with the information.
I'm really sorry. I'm still learning to deal so I don't have much advise for that but hopefully everthing will be okay.