Which kind of sexual exposure did you have ? If you had oral sex, you were exposed to herpes, syphilis and gonorrhea. If you tested for herpes more than three months after the exposure and your result was negative, that result was accurate. If you did it before expiring three months, you should repeat it.
You should also test for syphilis 6 weeks after the exposure and 3 weeks after the exposure for gonorrhea.
All the best.