I tend to think that if it's your belief system it's religion. If it's sombody else's it's mythology. Sometimes it is impossible to draw a line. Somebody else better do the line drawing, in this case - I'm not qualified. Myth is a structure of values, set into a story.
Religion is vastly other.
For some people I know religion is all about values. The Old Testament reads like myth to me. But myths also attempt to explain the structure of the universe too. The Catholic church seemed to decide those books were myth - or at least not religion. But surely the people who wrote those books thought they were talking about religion.