hi...so the problem is of erectile dysfunction..actually once a person has bad experience with erection while doing sex, he feels it shameful n that continuously bothers him psychologically. after this, every time before sexual intercourse he is worried about the performance and this worry exaggerate his problems. he became distracted while sex and this may cause loss of control over sex.. even when not doing sex person is worried about any major illness and worried that what has happened to me? why my penis is not getting hard? is there something serious with me? all these worries further exaggerate the problem... what u need to d is forget everything else..forget that u have lost erection before and u have erectile problem..when u feel relaxed, u ll focus and your erection will be sustained.. spend more time in foreplay...u can relax yourself psychologically by your own positive thoughts and exercise, yoga n meditation. relaxation therapy will also work.. medications have not significant role..but u can take anxiolytics to relax yourself like clonazepam 0.25 before sex..and if the problem is not resolving then u can go for viagra..but it is a last resort..u shud handle your problem without meds that is my advice,... i hope these advise will be helpful to you.