I had unprotected sex on a Thursday. I started to feel a discomfort while urinating on Saturday. In the 5 days since the pain has become worse. I thought it was chlamydia and took zithromax but the pain persists while urinating. It also hurts ejaculating and there is a constant pain in my penis right below the head on the underside. I'm only 23 years old. What could it be?