"My back is always hurt" is not correct English unless someone or something external is doing something to the back. In this tense, used with 'always', 'hurt' is a verb. "My back is always sore" is what this means surely. The phrase "always hurt" only works in sentences like "He always hurt her feelings when talking about her parents." Correct is "My back is always sore / painful."
So it's an aggressive back is it? Someone should get that back off your back!