Suggest Treatment For Pain In Lower Back And Front Hip Flexor Muscles

What kind of specialist should I see for chronic soft tissue pain? I had an MRI but got no information from it from the orthopedist about soft tissue. I have hip arthritis, but pain in lower back and front hip flexor muscles is the worst, making it hard to do any exercise even in the pool. I can do the physical therapy exercises but it hurts afterwards when inflammation kicks in.