hi welcome to healthcaremagic
there are many causes which can cause it..like- Drugs: Certain drugs, such as
steroids and drugs to treat inflammation,
high blood pressure, cancer, or
depression may affect male fertility.
Genetic: You may have been born with genes that may cause
infertility. A gene is a piece of DNA that tells your body what to do or what to make. Genes may affect sperm production, movement, and transport.
Hormones: Disorders in the testes may produce abnormal levels of hormones that may affect the production of sperm.
Immunologic: An immune system problem may cause
antibodies to be produced that may attack your sperm. The immune system is your body’s defense system against infections and diseases.
Infections: Chronic (long-term) infections of the male reproductive system, particularly in the
prostate, may affect male fertility.
Lifestyle: Smoking, drinking alcohol, and using illegal drugs may cause problems with sperm production.
Varicocele: A varicocele is a condition where the veins (blood vessels) in the
scrotum are enlarged and dilated (widened).
so find out the cause and get treated