"Kut" is a very rude word for vagina. It is street talk. It is often used to express negative feelings like disappointment or anger. In that case you can translate it with the F-word or Sh_t. The most decent translation of the text is: "How bad/lousy/crappy it has been, I gotta write it down". E.g. De film was (zwaar) kut --> the movie was (very) bad.