Over-reacting ... yes, but just because statistically the chances of catching anything is less than 1 per a few thousand times, there's still a chance.
For perspective ylinthe US about 1 in 1,800 people are diagnosed with syphilis in the United States each year (over 360,000,000 million people, and over 300,000,000 motor vehicles and over 400,000,000 firearms in private US citizens hands).
So you have a 1 in 84 chance of dying in a car accident in your lifetime, just to give you perspective. A big difference is syphilis can be cured with a little penicillin. Car accidents are another story, unless you pass the syphilis into the SO, then the car accident might be a better choice.
The time frame for taking an STD test varies based on the incubation period for the infection and can differ from person to person.
Treatment, various antibiotics, re-testing after treatment necessary to confirm not a antibiotic resistant case.
CHLAMYDIAThe average incubation period for Chlamydia is 1 to 5 days
GONORRHEAThe average incubation period for Gonorrhea is 2 to 6 days
SYPHILISThe average incubation period for Syphilis is 3 to 6 weeks.
HEPATITIS AThe average incubation period for Hepatitis A is up to 28 days.
HEPATITIS BThe average incubation period for Hepatitis B is 3 to 6 weeks.
HEPATITIS CTHE AVERAGE INCUBATION PERIOD FOR HEPATITIS C IS 8 TO 9 WEEKS.
ORAL HERPES(HSV-1) average incubation period for HSV-1 is 4 to 6 weeks
GENITAL HERPES (HSV-2)average incubation period for HSV-2 is 4 to 6 weeks
HIVThe average incubation period for HIV (Antibody) is 25 days to 2 months.
Molluscum contagiosum(MCV), incubation period averages 2 to 3 months and may range from 1 week to 6 months. Like herpes it's in your system for life, but the lesions can be removed removed surgically and/or treated with a chemical agent
Here's a rough estimate of the average number of single Americans you would have to have unprotected vaginal sex with to contract that particular STD.
https://markmanson.net/std-guide/amp