What Causes Pain In Lower Neck And Shoulders?

why am I hurting really bad in my lower neck and right shoulder? what is wrong with me? i am a 34 year old woman with three kids work and everything else a mother and a wife do...I work in an industrial setting doing repetitive motions all eight hours. I first thought that was the problem. but when I am off and have a day off or two, I feel even worse! I have tried medications, icy hot, ice, heating pad, etc. it hurts worse when I lay down, bend over, breathe in too!