Welcome to HCM
We understand your concerns
Sexually Transmitted Diseases are of several kinds and each one of them have their own ways of spreading from one person to another. Some spread through intercourse, some through skin contact, some contract through blood and saliva, some through sexual fluids etc. But the symptoms might not come this early. You said just three days. Symptoms of STDs might not come just in 3 days.
Anyway, to be sure consult a sexologist
or Gynecologist. Get well soon.