Symptoms 4 days after protected sex?

You get the most from this side when you provide detailed background information to support a clear question. Symptoms like what? Discharge/fever/ constipation/loss of appetite? It would be too soon to be pregnancy related, but timing might support a vaginal infection or STD.

You are best seeing a doctor in person. Please consider providing more details. What symptoms?

One can get symptoms after protected or un protected sex. If the symptoms never occurred before and are irritating you than see your OBGYN doctor.

The symptoms are not from being pregnant. Do a home pregnancy test 3 weeks after the episode of sex. If the result is negative repeat in 4-5 days unless you get a period by then. There is probably another reason for your symptoms.