Your argument inside with needs to match the method name for your relationship. In other words, if you do this:

$project = Projects::with("worknotes")->findOrFail($id);

Then, in order to eager load the relationships, your relationship's method's name needs to match:

// Note that I named the function "worknotes()", not "project_worknotes()".
public function worknotes(){
    return $this->hasMany("App\models\worknotes");
}

Both have to be called either "worknotes" or both have to be called "project_worknotes". Choose one or the other.

Next, if you want to get nested relationships, you can do that with the dot notation.

$project = Projects::with("worknotes", "worknotes.attachments")->findOrFail($id);