Cook pasta according to package directions, omitting salt and fat. Drain and set aside.
While pasta cooks, place flour, salt, and pepper in a large saucepan. Add milk, stirring with a whisk until well blended. Drop cream cheese by teaspoonfuls into milk mixture; bring to a boil over medium-high heat, stirring constantly. Reduce heat; simmer 2 minutes or until thick and cream cheese melts, stirring occasionally.
Stir in mustard, Worcestershire, and garlic; simmer 1 minute. Remove from heat. Add cheddar cheese, stirring until cheese melts. Combine pasta and cheese sauce in a large bowl; toss well.