Hello, Dr. This Is Really Embarrassing, But Last Night My

Hello, Dr. This is really embarrassing, but last night my boyfriend was about to ejaculate and i was ready to receive, then suddenly there was a huge flow of white fluid, and in the midst of it he realizes he was urinating. we both don't know what to make of it, but he claims that it felt really good. was he urinating instead of ejaculating? how was it that he was climaxing and urinating at the same time?