Hi Lisa, 

Thanks for your question. 
 
I'm sorry to hear of your aches and pains. 
 
At your body weights you are matched with a Medium spring tension to get the right level of support. We do describe the Origins Pocket 1500 model as very much a true medium feeling model in the top layers providing a slight sink but not too much. However, comfort is very personal and subjective so what's firm to one person is medium to another and soft to another. 
 

 
You are unfortunately well outside of the 60 day love it or return it guarantee that we offer; This is the time frame we give to adjust to any new mattress so any concerns with the comfort this is where we ask you to contact us. 
 
With that in mind, our best advice here is to solidify your slatted base with some standard sheets of MDF, plywood or pegboard. This should help to firm up the feel of the mattress as it introduces a uniform solid platform. 

Alternatively, we would also recommend checking a company online called Soak and Sleep. You disclose that you have tried Foam and Pillow toppers but we'd usually recommend something like wool or microfibres. Soak and Sleep now retail toppers they describe as firm so I would advise to spend time checking their products. 

Along similar lines you could also check out Latex Sense online. They have a wide range of latex toppers with different depths and densities compared with our own medium density topper so might be better suited to meet your needs. 

I hope this has answered your questions fully but if you do have any further queries please don't hesitate to contact our office on 0161 437 4419. Our office is open Monday to Friday from 8am to 8pm and Saturday and Sunday from 10am to 4pm. 

Kind Regards, Lee.