Welcome to HCM,
As per you, after period you had sex only once, that too with condom, thus there are no chances of pregnancy
. Otherwise also chances of pregnancy due to unprotected sex on 4th/5th day of menstrual period are very few. You are probably suffering with U.T.I. with/without Vaginitis
. You should get your urine tested for routine exam & Culture and sensitivity of urine & vaginal swab. You should drink plenty of water. Pregnancy test is not required at this stage. If there is delay in your next period, you can do pregnancy test.
Wish you good health,