Welcome to the forum and sorry you've problems like most of us here!
re the physio I don't do what makes me feel worse however sometimes anything will aggravate a tear or bulge to the point of feeling much worse. I learned over the many years of back pain to try and know when to rest and when to try something else.
Have you tried a Toradol injection for muscle spasms? That much might give a bit of relief and it's only a non steroidal antiinflammatory injection. Not the oral drug tho the injection has been helpful to me to reduce spasms/acute pain in both my neck and low back. I learned this of course after 2 back surgeries and many bouts of PT, drugs, lumbar epidurals and so forth.
I have also learned that I believe me more than what someone tells me I should feel be it a doctor, surgeon, PT or whomever. I mean when we're really scared we don't know what to believe tho you know how you're doing with whatever is going on when it comes to what makes you feel worse and what doesn't.
I have found the following website very helpful as a resource:
ChiroGeek's Home Page
re sitting.. couldn't do it for years so my last job was as a telephonic triage nurse/advice nurse and I had a standing station with a very thick mat on the floor where I'd stand (shoeless tho some good supportive shoes would have probably been helpful). At least I was able to stay at work an additional 5 years that way before I retired on disability tho I did have alot of pain tho not nearly as bad as if I tried to sit.
I think what might have helped me would have been to try lumbar ESIs earlier as well as pain meds. Maybe surgery tho I didn't want to go there again.
It wouldn't hurt to consult with several doctors and maybe to stop the physio if you think it's creating more pain than helping you at all. Sometimes it does start out that way and sometimes it's just too much and you have to find what works for you no matter what anyone else tells you will work for you in terms of exercise and strengthening. I found core strengthening using the stability ball easier on my back than anything else tho couldn't ride the bike, use the stairmaster, or treadmill and do a bunch of other things in regular PT.
Good luck and hang in there.