Thanks for your post.
As per your query what i would say is your backache which you are having will be most of the time when Sun in your natal chart is been influenced by an advers planets or poisted in an wrong position along with him when mercury as well been malefic. These sorts of problems might occur. My advice to you will be to share your birth details here to predict the root cause for your problem
coming to amber. Amber are fossils. Fossilized tree sap to be exact. Amber stone does not belong to a mineral family, it is more of a natural plastic and there is not an exact chemical composition that makes up amber stone. So my advice would be to opt for real gemstones(suiting your horoscope requirements) / alternative gem stone to come out of the problem.