I feel sharp pain in scrotum n lower abdomen during intercourse. pain is like someone hit the scrotum with force.

May be Epididymitis: As you are a male under 35 years old you could have any of a number of different infectious agents including Chlamydia trachomatis or Neisseria gonorrheae. As such you should seek testing and possible treatment for one of these diseases.

Testicles: It is likely but not absolutely related to a testicular problem - some possibilities include direct trauma, infectious process or partial torsion. Testicular torsion can lead to severe pain and loss of testicle. This is something you might want to discuss with a doctor who can examine you.