Talk to Gynecologist on Timing & Pragnance Issue

my performance is not good My wife says that my sex timing is very short I've always been like this, now he seems to have it all and baby does not conceive This is becoming a big issue in our practical life. my wife is 5 years older than me And for 15 years he is very happy with me And now suddenly she doesn't satisfy me Suggest me any such medicine or any diet plan, which can create a in my practical life. my first three children.And we plan to have another child and my wife Baby does not conceive I have no such medicine Please suggest so that my wife can be satisfied and she can conceive a baby.