What Causes Persistent Discomfort In Left Testicle?

hi doctor about 4 months ago i got mild discomfort in my left testical. I immediately panicked and went to the doctor twice and both times i was checked and told i was ok. I then went to a private hospital for a ultrasound which showed nothing was wrong. I still get the odd time when i have discomfort in my testical. then I can go for weeks with feeling nothing. I am at the moment suffering greatly from anxiety and taking tablets for this as last year i got divorced and lost my father. The discomfort seems to get worse when i worry. My doctor has said again that there is nothing wrong. My mum is getting checked this week because she has a growth on her lung so this is causing me so much more anxiety