I Have Pain On My Right Side On My Backside

I have pain on my right side on my backside that starts above my waist is most severe at my waist and at the top of my hip toward the middle of my buttocks but close to my spine up higher than my tailbone. Is this something to be concerned about? I've had it off and on for years, but now it is getting really bad. Sometimes it radiates higher up my back near my spine and the muscle is tight. I have a hip replacement on my left side and my entire left side of my body is weaker than my right, especially my left leg and knee.