What Causes Spasms In The Lower Back?

I have been dealing with acute lower back spasms for 5 days now. My dr diagnosed lumbar strain with spasm. I had been taking hydrocodone acetaminophen 5/325 every 6 hours with no relief, so we added ibupropen 1 or 2 tablets every 6-8 hrs, and cyclobenzaprine 10mg every 8 hours around the clock. Still no relief from the accute spasms occurring during sleep and upon arising from sitting position. I cut back and eventually stopped all the pain meds because side effects of swelling ankles, dry mouth, constipation, and fogginess were not worth it since spasm pain still just as severe with or without them. I m continuing the muscle relaxant (4th day). Icing has thrown me into spasms. Hot shower helpful mentally but not sure physically. Long history of pain from 2 herniated discs in lower lumbar diagnosed from MRI years ago. But this is only 2nd episode of spasms. I want to return to work so need a way to deal with the spasms. Any suggestions?