Bring a large pot of water to a boil. Season generously with salt. Add pasta and cook according to package directions until al dente. Drain pasta and return to pot. Stir in cream cheese and eggs. Set aside.
Place a large skillet over medium heat. Add the Italian sausage, onion, and garlic to the skillet and cook until sausage is browned and onions are soft, about 8 minutes. Drain excess grease and stir in 1 cup of pasta sauce.
Pour the pasta mixture into the bottom of a 9-inch x 13-inch baking dish.
Spread the sausage mixture over the pasta so it is spread out completely. Add cottage cheese over the sausage and spread over the dish. Next, pour the remaining pasta sauce onto the casserole and spread over the cottage cheese. Sprinkle cheddar and mozzarella cheese over the top of the dish so there's cheese in every bite.
Bake for 35 to 40 minutes, or until casserole is bubbling and cheese has melted.