I Fell Straight On My Butt Down Wood Stairs My

I fell straight on my butt down wood stairs my butt was complete black with bruise covering entire butt its been six months in constant back pain I've only had an xray my Dr. Asked me when I broke my pelvis I said never maybe from fall I live in 24/7 pain ins won't let me get an MRI until I complete physical therapy help what could be wrong
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