i'm gonna throw this into the mix:
is it possibly all 3???? i have piriformis syndrome (sciatica is the looser term), si joint pain, annular tear l3-4, and ddd l4-5. ALL but ddd were the result of an accident in 2000, but NONE of them are "connected" to each other (like radiation).
mine took 4 years to completely diagnose, so keep at it! i know we've shared info before, but wanted to give you some support if i could.
like others have said, if you could post the various diagnoses we might be able to pin down some ideas. i think the piriformis might be spot on, based on what you said. sounds just like mine. got some good "tools" for you, if you'd like. just let me know and i'll be happy to post what i do for some relief.
i'd also question & research ANY treatment recommendations. i know they're experts and all, but you need to FULLY UNDERSTAND why they're guiding you in a particular direction.
good luck, and keep us posted!