For a long time I was positive that I was an INFJ, because I fit the type description so closely. A friend, not a pro, gave me the test out of a book, which I know isn't necessarily going to give the most accurate answer, but at the time I knew nothing about MBTI and was taking the test "just because." (I did, however, take it seriously and answer honestly). Afterward, I read many descriptions about INFJ's and was sure that was me. Several months ago, I tested as ISTJ. I have read many descriptions of ISTJ's and I seem to fit that type also. Both types seem to be an equally close fit to my personality. I don't match any of the other types, and the only things in question are the S/N and T/F. I'm most definitely and I and J.
I'm wondering if MBTI type can change in a person. If it can, perhaps that's the explanation. I saw some things in myself that I didn't like, things that were causing distress to me personally, and I willfully made some changes. That may make it seem as though I'm an INFJ by nature, but I have forced myself to behave as an ISTJ, and that's a possibility I've entertained. But I'm not so sure that's what happened. It may be that I behaved as an INFJ but finally gave myself permission to be my true self--an ISTJ.
How can I figure out my true type when I'm so close to both?