Krak I have an L5-S1 fusion and know all about your pain. I lived life with a broken back for a couple of years due to a dumbass misreading the Xrays.
Take it easy, you probably didn't blow everything out like they say in one fell swoop but who knows. Call your insurance and find out what they can do. Complain to them about the pain and see what they can offer. Get a good contact at the insurance company, even up the nurse level, this can help.
Some of these injuries will right themselves (enough anyway) in time. The back can take what seems like forever.
I also know about life halting with the physical restrictions...and that sucks. My fusion surgery had immediate relief years a go but now I deal with chronic neck issues.
It might be worth it to pay for the MRI, if bad enough and if the symptoms are bad enough. But if so, then don't let the doctor's office push you around.
Remember, the squeaky wheel gets the oil.
As far as medicating, try some different chronic, I suggest indica with a high CBD content but there are so many kinds of bud. One may work well for you in the worst times.