Are your periods regular? Secondly was the intercourse protected or unprotected?
These symptoms can be unrelated to intercourse,it might be just simple viral infection giving you the above symptoms of fever
and sickness n tiredness
Regarding brown discharge this could simply be a sign of ovulation or implantation
bleeding that means you might be pregnant. Wait for your natural cycle and if they are delayed get a urine pregnancy
test done, and consult your doctor for fever and get the relevant tests done.