There can be various reasons for your lack of performance, but first you have to identify whether it is lack of erection or premature ejaculation or lack of excitement. There can be psychological or physiological reasons. First analyse if ur nocturnal erection is good or not. If not then u have impotence which needs medical attention. if its premature ejaculation then u can try Master Johnson method. Its basically foreplay without use of genitals. Also if ur obese n smoke or abuse substance then it s better you quit n have moderate exercise daily. Abstinence from masterbation can be helpful. Try these n I hope u have a healthy sexual life