Back stiffness

Hello ,i have extremely stiff muscles on the right side of my back ,i strech the muscles with relief for a few minutes and it goes tight again ,when these muscles are stiff it causes my right side of my body to hang as if its shorter than the left side ,the muscles goes shorter almost like its coiled up . I have had this problem for well over 4 years ,i’ve diagnosed myself wrong for many years and now i’ve finally hit the nail on the head but I don’t know how to loosen these muscles permanently ,any help would be appreciated ,im 19 years of age ,male