Help with a mattress for chronic back pain

I suffer from myofascial pain syndrome, a fancy name for damaged muscles in the back, I have painful trigger points in my shoulder, neck and lower back. We bought a bed last year from Bensons with a latex topper on it and sadly it makes my lower back pain much worse after a night sleeping in it, so it has been moved to the spare room. I am extremely wary about investing in another mattress as we are still paying for that one!! and do not know which type of mattress to choose, so any help or advice would be greatly appreciated. I weigh 9 stone and my husband weighs 13 stone. We recently went on holiday and the bed seemed much better for me, it was 80% / 20 % ratio of Natural Latex. I am desperate for some advice on a mattress that will help me to sleep and not wake up feeling 100 years old. Thank you in advance
Nicky