Why would the tail of the epididymis swell up with no pain and then go back to normal after only minutes? Also I have heard that the tail of the epididymis can get bigger during ejaculation. is this a normal sign? Do cysts change in size with fluid and throughout the day? I am more concerned that if it is a blockage of the epididymis or something when ejaculating that it would cause infertility for certain?