Have had this Sealy Laytex mattress for just over 18 months and I seem to be sinking on it. I'm 14 st and have a normal single base with 2 drawers. I'm five foot 4 I've purchased one of your Artisan natural fibre mattresses on the advice of a lovely chap called Guy who was wonderful and so patient. I've chosen a medium one. Have I chosen correctly? Val from Aberdeen