what's the best way to sit up in bed?

Whenever I'm using my laptop whether it be working or watching Netflix, online shopping etc.  I do it while sitting up in bed, I prefer bed over a desk or couch but I find myself sitting there for hours at a time, i take toilet breaks very often as drink a lot of water while doing whatever it is I'm doing at the time but I can't seem to find a comfortable position. The bed itself is super comfy but I no matter how many pillows for positions I try, I get a sore back.