Place chicken breasts in bottom of slow cooker.
In bowl, combine both soups, broth, and seasonings. Mix well.
Pour soup mixture over chicken.
Add diced onion and bell pepper.
Cover and cook on LOW 6-7 hours until chicken is tender.
Remove and shred chicken with two forks.
Return chicken to cooker.
Add broken spaghetti, stirring to submerge.
Cook on HIGH 30-40 minutes until pasta is tender.
Stir in cheese until melted. Add milk if needed for desired consistency.