Hi thanks for contacting health care magic..... You should consult psychiatrist for detail history and physical examination... Your history taken for smoking , alcohol habit etc.... Your blood pressure checked as hypertension can lead such problem.... Investigate with random blood sugar , serum cholesterol for rule out diabetis and hyper cholesterol. If you have excess stress or depression in routine life then also problem can be there. Take healthy diet and more fruits Vitamin A , E helpful as rich in antioxidant. Do some fore play and be relax while sex Regular exercise done.... Do sex in comfortable position.... If still your cause not clear then serum testosterone and prolactin estimation done. Consult psychiatrist with keeping this answer in mind . Take care