In a large pot of lightly salted boiling water, cook the spaghetti according to package directions.
Before draining the pasta, dip a glass measuring cup into the cooking water and measure out ½ cup of the water; set aside. Drain the pasta and set aside.
In a medium mixing bowl, combine milk, salt, pepper, and eggs, stirring well with a whisk to mix. Gradually add reserved hot cooking liquid to milk mixture, stirring constantly with a whisk.
Cut the bacon into small pieces with scissors. In a large nonstick skillet over medium heat, heat bacon with the garlic, stirring to keep garlic from burning, about 1 minute.
Reduce heat to low, and into the skillet, add spaghetti, milk mixture, and peas; cook, stirring constantly for 3 minutes, or until sauce thickens.
Add cheese, tossing well to mix.