You should really invest. Your sleep will improve 1000%.Every time I mention getting a new mattress, my husband says no. It probably would help my back, but {shrug}. Wed just get an old-fashioned one anyway.
The tech for making mattresses has advanced in the last quarter century. You should look into it. Even the most basic mattress will be an upgrade for you.
It's not like you can install Linux on it and give your mattress another 5 years of life.