A sack is a heavy, plain load, so it stands for burdens carried and work that must be done. Folk tradition also links a full sack to stores gathered for the future.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.