I get azoospermia

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How to diagnose the cause of azospermia?

You need to consult a doctor to examine you quite well and to require some tests that are mandatory to diagnose the cause of this symptom.
At first you need to do Sperm analysis again, and also you need to do testosterone test, and testicular biopsy.
Other tests to do include:
CBC, ESR, CRP, Full chemistry profile

Is azospermia curable?

Well, I think this depend on the cause. If the cause is manageable in this case azospermia can be treated, however if there is no treatment then I feel sorry to tell you that there is nothing to do now. 

Can you be able to have a child?

I believe you need to do testicular biopsy to answer this question. 
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