Hi there. Gosh, to be honest, I don't know how quickly the white blood cells will not be in your urine after infection. You were on antibiotics, which should knock out infection, right? You could also have inflammation of the urinary tract which would result in white blood cells in urine, but bacterial UTI is the most common cause. Some women have Sterile pyuria which is persistent white blood cells in urine without any bacterial infection at all. That's not super common and usually having white blood cells means UTI or kidney issue. They will likely check you for these again. How can you test for these on your own at home?
Do you see your doctor today? Let me know what they say!