Readjusting to futons

Having just spent 5 months sleeping on a bed in my home country, Ireland, I have to once again readjust to sleeping on a futon. My Mom always had the best mattresses available . They are very comfortable and supposed to be good for your back. Despite that, my body seems to do better with futon! 

I do prefer the height of a bed, but after a month of living in Ireland, I started to get a pain in my back. I'm pretty sure it was from sleeping on a thick bed mattress, after years of sleeping on a thin futon on the ground. However, I don't think my body will suffer from readjusting to a futon now. I think futons are better for my back, for me personally, but it's probably different for everybody. 

Do you ever get back pain from changing the type of bed you sleep in? Which do you prefer and / or find better for your back - a mattress or a futon?