What Causes Severe Pain In Lower Pelvic Area Along With Constipation?

I have had pain in my lower right pelvicarea. I had a complete hysterectomy 7 years ago. The pain hurts and I am having difficulty passing gas and having a bowl movement. After passing some gas and having a bowel movement, I have had severe pain and burning in my lower or is leg and groin area. This happened before and went away. When I walk it is very painful and I feel pressure and pain. I still fell pain when I lay down but not as bad.