Cook chicken until fully cooked, add peppers and onions. Cook over low heat until peppers are soft, but not mushy. Add the fajita seasoning while the peppers and onions are cooking.
While cooking the chicken mixture, boil the fettucine noodles.
Also, in a small pan mix together cream cheese, butter and milk, let all melt together, add parmasan cheese. Do not let the cream cheese mixture boil....you will scorch the alfredo sauce! If the sauce seems too thin add more parmasan cheese.... (the more cheese the creamier the sauce)
When everything is done mix all three things together. Stir and serve. I usually serve with salad and some sort of bread.