Should The Antibiotics For Urine Infection Be Taken After Menstruation?

Hi , i have been examined pus cells in urine.Doctors advised me to take antibiotic & asked for urine culture.When the repot came out the doc however discontinued that anti biotic & suggested another however she asked me to take them only after my periods ..but i have not got period yet & i think i am pregnant..what should i Do ?? please advise