Work and RA

Hi, this is my first post as I have only just been diagnosed with RA having seen a doctor and blood test due to having the typical symptoms of early RA.

I wonder if anyone can help me regarding my questions concerning work. I do work which basically involves driving a HGV vehicle in order to deliver rather heavy items to businesses or domestic property. I struggled a little on one day last wee, and coped during the others. I had a couple of days off around September due to shoulder pain which I thought was a frozen shoulder but I'm wondering now if it was the onset of RA as it was a recurring pain. Anyway, if I would be unable to carry on with my employment, is it likely my employers would find me another job within the company. It's a large company. I would say a household name for what it delivers. And recently, due to the driver shortage, they have increased my wages twice in a year so the pay is pretty good at the moment. If I was assigned to another type of work, could they then lower my wages if the new role was usually payed less?

I haven't told my employer yet as I would like to see how things transpire. I am supposed to visit the rheumatology department of the local hospital in the next couple of weeks my doctor said. Incidentally, my employer does apparently have a HR department and there's at least one occupational therapist I believe the title is.

I am not a member of a trade union which I now regret for their support.

Any help would be much appreciated.