Open Question: why am i getting pain in my testical?

Hi I have recently went to see my GP about pain near my left testical ( not actuallly on it ). He said it was an infection of the tube that carries the spern to the penis, the antibiotics he gave me worked great and the pain went away for a wek or 2. However its started to come back not all the time and it spreads to my lower tummy. The pain is very manageable, but what could it be. It also hurts slightly when i ejeculate above my left tetical. He has sent me for an ultra sound, but said there was nothing to worry about? Should i be woried,