Cook pasta until tender but firm, about 18 minutes. Drain thoroughly. Place shells in a single layer on greased aluminum foil to cool. For filling, mix beaten egg, cottage cheese, mozzarella cheese, Parmesan cheese, parsley, and oregano. Fill each shell with about one-fourth cup filling. Small scoop or spoon works well. Place filled shells in 9x9 baking dish. Mix the tomato sauce with the undrained diced tomatoes. Pour evenly over shells. Cover with foil and bake 15 to 20 minutes at 350 degrees. Remove foil and bake for another 10 to 15 minutes or until hot and bubbly.