Finding a new job is impossible!

I was diagnosed with axial spondyloarthiritis 9 years ago and have been progressively getting worse. I am a healthcare professional and I am on my feet for up to ten hours a day. Due to the levels of pain I only work two days a week but this is getting harder and harder to achieve. I have been looking to find a desk based job for two years now and only made it to an interview stage once which i unfortunately didn’t get. I have a masters degree and have so many transferable skills but no one seems to want to employ me. Has anyone had any similar experiences- should I mention the reason for my change of career in applications but I don’t want to put people off thinking I will be off sick all the time as despite all my ailments I very rarely take time off and never have for the arthritis. I can understand why people question why I am giving up a good job to be paid a fraction of the hourly wage but how do I get someone to take a chance on me! Any ideas gratefully recieved!