Hi there I have had a problem with my testicles

Patient: Hi there.I have had a problem with my testicles for a while now! My left has shrunk to the size of a pea where my right is perfectly normal. I used to have a pains now and again a while back but don’t get them any more. Also I cannot get an erection either and when I do is only when I masturbate; but then it shrinks so fast when i finish/stop. I’m so worried and thought I could get some advice before going to the doctors!Many Thanks.

Doctor: