You know what worked for me? New wardrobe, and traveling.
When I was 15 I was really ugly, I thought. My sister convinced my mother to give me $300 for new clothes of a style that was my choice. But laid ground rules about no sports teams, sweat pants, pajama bottoms, stuff like that. We shopped from 10AM-9PM and finally got myself a brand new wardrobe for my trip down to Florida, where and when I got my first kiss.
Than at 17 and 21 I went through another stage. I couldn't attract a woman to save my life, but knew I was attractive. So at 17 I went to a conference for a week in Washington DC. 50 guys and 250 girls. I was rated in a slambook as #4 hottest guy. That really soared my confidence. And at 21 I went to Florida and worked for Disney world in their
College Program (they also have a career start program for kids graduating high school) and I met so many great people, went to so many great clubs and made out with a different girl seemingly bi-weekly.....by hardly trying lol.
Seriously if you send me pics of him and his style I can give you some "preppy boy" tips on how he can dress (as this is my style). I also worked for AE for a year and got to love fashion. (an aside, best freakin job ever. Girls would look in mirrors and ask me if their ass was fat....and I'd always say "yes, pretty hott and temptin'" only got one complaint and 8 phone numbers....sexy plexi)
Otherwise just try to hook him up, or talk to him. Ask him why he feels the way he does. He's obviously in-tune with his emotions if he'll talk to you about them.