What Could White Puss Build Up On Penis Suggest?

I have white pus which build up along my my raphe on my penis. It is not normal though several doctor.s have told me not to worry about it. It comes out of a small pinhole opening along the raphe when I squeezz the area where it builds up. I've had cultures which have come back negative for an std. however I noticed it a few days after a sexual encounter. Do you have any idea what is wrong with me? I have been to several urologist who have told me there is nothong wrong with me They are wrong I will continue to go to doctor after doctor until I get anwsers