What Causes Pain And Pus Discharge From Penis?

Hi. I am a 22 year old male homosexual. I have been with my boyfriend for 2 and a half months. In this time I have not had sex with anyone else. For the past two days I have had a slight irritation inside my penis. And this morning There was a small amount of puss come out of the inside of my penis. I am very worried about this and do not know ahat to do. Can you help me?