90% of people that are positive for syphilis will show antibodies at 3weeks I would believe your test and move on
I would worry about herpes. And if all you had was oral there was little risk and no need to test
By the way the igm test for herpes is unreliable
Did you get a different kind of test for syphilis? It should say RPR or VDRL, or FTA-ABS, but not IgG.
I also wouldn't worry about either that much, but if you feel the need to test, make sure it's the correct tests. https://www.webmd.com/sexual-conditions/syphilis-diagnosis
And yes, the IgM is unreliable for herpes.