Have you got previous heavy manual work as a cause or just recent work?,only asking this as if you have history of aggravating these joints/discs then you need to take this seriously. Maybe back to trad cleaning
A bloke i know well has been going 11 years trad,running an 09 transit van(no signwriting),thinks wfp is complete crap/nonsense,he works with 2 helpers(probably,not definitely, cash lads). He gets to stroll about cleaning downstairs windows and collecting money if the customer is in.No,he isnt strolling about he is doing plenty he just makes it look easy. I watched his team this week going down the road my mother lives in, bungalows,many are dormer. They were like poetry in motion,carefully watched them clean the leaded dormer across the road,£8,i would want £12.Gutted i didn`t time it but it was quick,i estimate 6 mins max and saw him get the money.Couldn`t fault the cleaning methods it was just fast and slick. At a very conservative estimate they are running at £50/hr. 6 hr day gives £300,£50 each for the lads(maybe more),thats £200 notes cash for the boss. Alright maybe not every day is like that but if he isn`t grossing £700 a week for himself i will eat my hat,nice bloke and a grafter he seems to have his head screwed on right in my opinion. Point i am trying to make is he can probably control or put a limit on how much exertion his back might be taking as he pleases whilst still enjoying a very good income.