As you already know that there are no sperms in your semen, but it doesn't prove that your body is not making sperms. Sometimes sperms are made but they do not reach semen.
You need to consult a urosurgeon. After treatment sperms may reach semen. Or if they don't then doctor may be able to harvest your sperms and put them in your wife's uterus
And last if nothing is possible then go for donor sperms.
There are a no. of options for you, so don't be disheartened and follow your doctor's advice religiously.
Hope for the best.