I think he's too young to just start with the prescriptions.
Are you healthy? Are you under some stress? On
antidepressants? What about when you masturbate? Do you get a good erection then? How do you masturbate? Is it with a really hard grip or by rubbing hard on something? Sometimes guys who get in the habit of masturbating with a "death grip" can have trouble with intercourse because it feels so much more gentle.
But do go to the doctor and have a physical. A guy your age should not be having ED. There may be some health problem that's causing it.
Good luck!