Hello, I read your message carefully and understood your trouble. First, let me ask if you have other symptoms. Fever? Pain? White cells in urine indicate for infection. Women are more predisposed to develop urinary tract infections and even if there are no symptoms at all urine test shows a light infection. Having sex can be considered a kind of trauma and it can affect the urine test because a little bleeding may happen. The first portion of urine shows the bleeding coming from the urethra. As in women urethra is short, your doctor needs to see if the bleeding comes from your bladder or not and for that has ordered you to send to the lab the middle portion of urine. My advice is to send the middle portion to the lab and repeat the test after one week. Mention to your doctor if you take any blood thinners and if you do any strenuous exercising because they may cause urinary bleeding. Hope this is helpful for you. Dr.Albana