Whilst we can't give medical advice, if you are looking for a softer feeling bed, you may prefer the feel of latex, which has an instant bounce to it so allows easy movement. Also, the less springs that there are in a bed, the softer the feel.
Therefore I would recommend you try a Pocket 1000 Latex. Alternatively, the Sanctuary 2400 Latex with an extra layer of mini springs has a luxurious feel that will really support your shape.
The best advice we can give is that you go into a store and try a few beds for yourself as comfort is very subjective, this would be particularly important for you as you have special requirements.
Click here to enter your postcode to find your nearest stockist. It may be worth phoning ahead to check that they stock a good range of models for you to try.