Q: one of my documents suddenly converted to plain text can't get it back. it had charts etc all over it. have been working on it for about 5 months lost a lot of work. Help. can i get it back?

Are you using Time Machine?  Otherwise no other help.

TextEdit/Preferences/New Document - Rich Text selected?

Open & Save/When Opening a file - the 2 settings unchecked?

Did you make ANY other backups at all? How about an earlier copy?

If not, I highly suggest you take this as a cautionary warning (but clearly a disaster for you) and either obtain a separate storage drive to set up Time Machine on (it's ridiculously easy), or at least keep a duplicate copy of important docs you're working on every time you make major changes.

Don't kick yourself; It's happened to everyone at one point or another.

Sal