I've figured out why it is that I doubt my type:
I essentially struggle with socionics LII descriptions: "I know I have strong 'Ti', but why doesn't it match socionics INTj descriptions at all?" I know the answer: in MBTI, I am INTP. I fit a lot of the descriptions almost perfectly. E.g.:
http://personalitypage.com/html/INTP.html. However, socionics LII descriptions don't match the INTP descriptions at all. Why? Here is the difference between MBTI INTJ and INTP:
INTJ: Precise, self-confident, reasoning is more practical, more structured/organized, more practical about logic/career.
INTP: Less precise, plagued by self-doubt, reasoning is more theoretical, not organized, more innovative about ideas/career.
If you look at these two descriptions, INTJs are judging types, but they sound more NiTe (or TeNi) than TiNe, while INTPs are the exact opposite. Therefore, in socionics, INTJs match up with LII descriptions because they are structured, organized rational types, but INTPs might match up better functionally, because they are more realistically TiNe. Therefore, in my case, I am 'LII' because I am TiNe - not because I'm structured and organized. The discrepancy then comes from the descriptions - as I said, LII descriptions seem INTJ, but not really TiNe to me. Therefore, because functions are probably more important than descriptions, I am most likely LII, but I simply don't fit most of the descriptions. That might then explain the confusion I have been having. I hope that helps...