Bring a large pot of water to a boil and season with the sea salt.
Add the whole wheat spaghetti and cook according to package directions until al dente.
While the pasta cooks, place the diced pancetta in a large skillet over medium heat and sauté until crisp and golden.
In a small bowl, whisk together the eggs, egg whites, grated parmesan cheese, and black pepper until well combined.
Just before draining the pasta, reserve about 1/2 cup of the starchy pasta water.
Add the fresh spinach to the skillet with the pancetta, stirring for 1 minute until just wilted.
Drain the pasta and add it directly to the skillet with the pancetta and spinach, tossing to combine.
Remove the skillet from the heat immediately to prevent the eggs from scrambling.
Slowly pour the egg mixture over the pasta while tossing constantly, adding a splash of reserved pasta water as needed to create a smooth, creamy sauce.