How do you keep from feeling so darn lonely?

I am a married 39 yr old woman. I work full-time. I have 3 children. One is still at home. I've been married 12 years. There is absolutely no romance or affection in my marriage. Everyone says thats normal in a marriage. But, I am finding it hard to live with. I guess I need to accept it and believe me I try. But I still get so lonely. Anyone have any suggestions to kep from feeling so darn lonely?