This happens with drugs such as alpha blockers (Flomax, etc) which relax the prostate and surrounding muscle. I had this happen while on Flomax with a painful inflamed prostate. My urologist was actually pleased to hear this, as he siad it showed the drug was working. However, as he also felt it was important to be able to empty the prostate frequently, he switched me to a different drug which interfered less with ejeculation. You should discuss this with your doctor, and see if an alternative is right for you, too.