Work trying to change my work pattern :(

[strugglingstepdad]

I work as an hgv driver for a largish company.

I have a regular route, but recently took on a second route as a temporary measure to ease the workload as we were short of drivers.

I've been off work for 2 weeks with a bad back.

Today I had a phone call from one of my supervisors asked no when I was returning. I told him I had a docs appointment tomorrow (was signed off by a nurse practitioner but told to get a gp appointment).

I told him if I was returning to work this week then it would have to return to just my original route as I am not risking more time off. My first route is about a 7 hour day, the second route pushes it up to around 12-13 hours. All of this is within all working time and drivers hours laws as neither are exceeded.

He responded that that wouldn't be possible, it was either do both routes together or change shift pattern. As it stands I get 1 weekend day off per week and a weekday, but if they change my shift pattern then I lose my weekend day off and have 2 weekdays off :(

I really don't know what to do! We currently don't have a transport manager as he left and there's a recruitment freeze until January so I'm a bit stuck :(