Mr absent and I looked after my mother after she broke her hip, knowing that she would never be able to return to her previous independent life. (We moved her in with us straight from the hospital exactly four months to the day after we got married.) The strain did begin to get to me at one point and I was visiting my GP about something else all together when I started shaking and burst into tears. She was the one who recommended help from carers and put the whole thing in place with social services. They couldn't do a lot as they didn't have a huge amount of time, but their help washing her hair, getting her dressed, giving her breakfast, even making her bed took the pressure off me. So I would recommend a word with your GP.
As far as respite care is concerned, I think you have to be a bit firm with your mother. However, I would recommend checking the home that social services suggest. The first one we used was a truly horrible place where my mother contracted MRSA while we were away and I came home to find her being admitted to hospital where she stayed for three months in a heart-breaking condition. The second one (used a couple of times) wasn't luxurious but was okay, clean and full of kind people. My mother's big fear was that we would dump her in the respite home and never collect her – not that she ever had the slightest grounds for believing that. I suspect it was memories of days when the workhouse and then those horrible geriatric wards still existed. If that's the case with your mother, do you best to allay her fears. And, by the way, I wrote to her every day that I was away, including the day I left the country, to reassure her that I loved her and would be seeing her soon. (She kept every one of those letters, bless her heart.)