That's hard. I know I did a lot of reading to help myself with my self esteem and feeling like I didn't fit in as a young adult. I saw a Philippino therapist for 20 years (I'm not adopted or from a mixed-nationality situation), maybe you could find a Korean one to see for awhile who would understand and could help you feel better about yourself?

http://www.mitaliperkins.com/bookshelft.html