I don't think that works either, unless the "oder nicht" is emphasized? Actually don't ask me I have no idea xD
In my mind "doch" translates to "though" or "but" a lot. Like "Das hab' ich doch nicht gesagt" - "I didn't say that though" or "Ich verstehe doch" - "but I do understand".
I never learned it in a formal course or anything though, I just kind of picked it up from hearing other people in Germany using it. Same with "noch", which has like 4 or 5 different meanings in English.