How do I find out qualifying for benefits?

I retired from teaching due to ill health a year ago aged 57 and receive a pension. It's ok but will need supplementing later. I have some lingering illness and not working now, but not necessarily connected to the original illness - so I might find it hard to get a doctor to say I can't work on that basis. But I am finding prescription charges etc are higher than I want. How can I find out how I can qualify for any benefits or concessions, I'm a bit new at this.