Your equipment is working. That means you don't have erectile
dyfunction.
The sin seh can't fix what is not spoilt..
Your problem is anxiety.
Sex starts in the head. The upper head. It sends stimulus down
to the lower head. A lot of things can interfere with this.
Stress at work. The effect of an argument or quarrel at
workplace can last for hours in you brain. Unresolved problems at
work also interfere with the mind. When you leave the office,
leave everything in the office.
Performance anxiety could be another cause. Wanting to be the
super stud will have the opposite effect. Let her bj you until you
cum, then eat her until she cum. Let it be at that.
Frequency. Hey! you only have so much seminal fluid in your
balls, phase out your sex and your masturbation. She can cum all
she wants, while you have only a few shots and you must wait to
reload, this takes time, sometimes days.
Try not to use too much tissue paper to wipe your lower head.
The white toilet paper contains too much bleach, and over
time, this may desensitise your lower head.
The SGH doctors should have refered you to a sex guru.