Hi Margaret Douglas, 
 
Thanks for your question, 
 
At your height and body weight, you require a medium spring tension. This is the correct tension to support your body weight.
 

 
Orthopaedic mattresses are generally very firm, and at your body weight would not be ideal. This is why you are experiencing the pains you currently are. This is due to the top layer of the mattress not being soft enough to allow your body to sink into the upper layers of the mattress when you are trying to sleep on your side. 
 
I would recommend taking a look at the Origins Pocket 1500 or the Artisan Naturals in medium spring tension. 
 
Both of these mattresses are a medium in the upper layers and are ideal for side sleepers as they will allow your shoulders, elbows, hips and knees to sink into the upper layers. The main difference between the two is the natural fibre count. The Artisan Naturals contains 85% natural fibre, this will assist in dissipating any heat in the mattress. You also then have hand sewn side stitching, hand tufted and vanadium calico encased pocket springs for a superior level of support. 
 

 
The Origins Pocket 1500 is the best seller in our synthetic fibre range with an initial natural fibre comfort layer. This is more budget friendly due to the synthetic fibres used. 
 

 
I hope this helps if you have any further questions please don't hesitate to contact the office on 0161 437 4419