Hello,
The numbness can be due to the pressing upon of the nerves by the varicocele. For the same I suggest you to consult a surgeon and discuss the treatment options with him. For the pain, you can provide support to the scrotum by wearing an athletic supporter, apply ice to the scrotum, take warm baths if there are signs of inflammation, while lying down, place a rolled towel under your scrotum or try over-the-counter pain relievers, like acetaminophen or ibuprofen.
It is true that uncontrolled diabetes effects fertility. But I suggest you to have diet control and indulge in plenty of exercise which are helpful in early diabetes.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
I have some early diabetes.... I just don't know how I can become impotent and a eunuch so young? it has just destroyed my motivation and energy for life