Hiya
I really can empathise with your frustration - I am naturally a very active person and often get frustrated (occasioanally to the point of tears) that I can't do everything I want to.
Someone at work commented that my mind is cashing cheques that my body can't honour - so true.
Maybe if you're not up for full on swimming you could go along and do some stretches in the water? The water will support your weight. You could also just walk up and down the pool rather than swimming - easier exercise when you're in pain but at least still moving around. I quite often do my stretches in the shower as I find the warm water comforting and makes the stretching a little easier - my housemates sometimes get grumpy with me and say I'm hogging the bathroom mind you, they're not very good at fishing their long hair out of the plug hole so I think we're more or less even!
During a recent bad flare up I was very upset about the whole fibro thing and cancelling fun things left, right and centre. My mum suggested that I find a hobby that I can do when I'm too poorly to do my normal things. Great advice - I nowhave a 1000 piece jigsaw and a sketchbook, drawing pencils and pastels. I am rubbish at drawing but I find it relaxing and enjoyable and as for my jigsaw - I am addicted! When I was needing to stay in and rest it was really good.
I really recommend that we all learn to talk about our fibro and its limitations - I have found that people are much more understanding if I have talked openly about our condition and how it affects me. It is difficult to do but I think the effort is worth it. When I talk about fibro to people I really try to state things in a factual way without complaining and also remembering the balance between saying enough to put my point accross but not saying so much that I'm marked as a hypochondriac.
Good luck and hugs
Chocchip