What mattress would suit me?

I'm 6ft tall and weigh 11st, so skinny & bony, currently sleeping on a 4ft6in wide Highgrove Euphoria (2000 pocket series non turn encapsulated mattress / 100% latex/ bamboo yarn). Advised this was a medium support mattress but I am suffering from pressure pain in my shoulder which disturbs my sleep. Could you recommend a replacement mattress?