You sure you never used aas? SERMS (clomid, nolva) can also upregulate SHBG.
Without obvious reasons is really difficult to pinpoint what triggered the issue.
Having chronic low iron myself (even with normal CBC) I can relate to that.
I know this simply because my partner had it during pregnancy.
Its then that I discovered that Anaemia isnt simply Iron deficiency, but can have several causes.