Left buttock pain

Patient: My left buttock beside the coccyx region is swelling upon compression (sitting) and causes inflammation and discomfort. Upon sitting for long time total left buttock is swelling and It takes one hour to get relieved. After day’s work there is much inflammation ( I can not say it is pain) and pulling like pain (like after taking injection we feel it for some time ) and by the morning it is free. I have been suffering from this for the last one and half year. I used many pain killers and muscle relaxants but there is no use. I have taken MRI and Bone Scan of lumbar Spine. Doctors say that everything is fine. They say that the muscle week and advise me the muscle strengthening exercises.Please help me to get relieved from this problemThanksRama Rao.

Symptoms: Swelling, inflammation, Pulling, Becomes hot