Your symptoms are not those of any STD, and in any case the chance of catching an STD from the exposure you describe was zero, for practical purposes. I don't recommend testing at all, but if you insist, wait until at least 3 months after the event before you have an HSV-2 test.
1) If you have had no sex with anyone else since you were tested 18 months ago, the most likely explanations would be a) your earlier test was falsely negative or b) your new test is false positive. Both of those are more likely than the chance you acquired HSV-2 during your exposure 2 weeks ago.
2) HSV-1 isn't normally an STD. In any case, why would you waste your money on a repeat HSV-1 test? Once positive, you'll have a positive result for life.
3) No.
4) For sure "another case of nerves", nothing more.
HHH, MD
Thank you!! Just a point of clarification - if I have oral HSV-1, and somebody who also has oral HSV-1 gives me oral sex (oral-penile contact), can HSV-1 be "reintroduced" genitally? In other words, even though I can't get it again, might it take up residence in an additional part of the body through this mechanism? I'm sorry if that's a silly question, but it's what I meant to ask before.
Again, many many thanks - you perform a really outstanding public service here, and I know we all appreciate it (and you) very much.
People are highly resistant, if not completely immune, to a second HSV infection (of the same type). This has been discussed many times; search for "genital herpes" and "herpes transmisson".