I wonder if you have a fractured tailbone?
Was that included when the surgeon was looking into the other back problems?
I don't think intercourse itself would have injured the tailbone, unless there is a fracture or arthritis...
but I'm just guessing ...
One of my boys bruised my tailbone or fractured it during birth, it mainly only hurt when getting up or sitting down - the pads
& pressure on & off it mostly - took about 2 weeks to recover.
Is your hurting constantly? or on/off?
surgeons do prefer to do the surgery and send you back to primary care , but I would think a really good one would at least rx some therapy as follow up...