My district manager pulled me into the office and gave me a hard time about my condition. Advice?

Thats awful, get as much external support as you can. Work bullies of all kinds thrive in the dark .

Do you know about this relatively new service ? https://www.england.nhs.uk/south/2017/05/08/new-occupational-health-service/

Like others have said it's about reasonable adjustments to enable you to get on with your job.

Good luck !