Ankylosing Spondylitis, Chronic Fatigue and Exercise

Wondering if there are any other members on MFP that have A.S. and is also lucky enough to have chronic fatigue as a side effect? If so, do you have any advice on how to get your energy up? For the past two months I have taken up swimming, at least 4 or 5 days a week. Swimming has REALLY helped with the A.S. pain, but I've found that swimming and even walking is just draining what little energy I do have and I have been run down far more than normal which makes it even more tough to exercise...any suggestions or ideas to change this would be awesome!