I believe you have some INFj like tendencies, however I have to confess that I now think the others were probably right and that you might not be an INFj afterall. Perhaps the INFp socionics type maybe more suitable for you especially since you said you have sometimes tested INFJ in MBTI. Good luck in your finding your type.

http://www.socionics.com/prof/infp.htm

http://www.socionics.com/prof/infj.htm