I don't know very much but I believe that there are several factors that could contribute to an early menopause.
The general rule is that if your mother naturally ceased menstruating at a normal age (i.e. between 45 and 55) then you're likely to follow the same pattern. If she had a premature menopause (i.e. before 45) then you are not necessarily going to follow suit - genetics account for about 5% of early menopauses.
HOWEVER, many of the other factors that contribute to premature menopause, such as cancer, autoimmune conditions (e.g. arthritis, rheumatism) or chromosomal problems, may also be hereditary.
On the other hand, other factors that contribute to premature menopause, such as smoking, surgery (for endo, PCOS or other) or rarely, infections such as mumps, are specific to the individual.
Unless you know that your mother's early menopause was caused by a medical condition which you also share, I shouldn't worry too much - your chances of a similarly premature menopause are 1 in 20. But if you don't know what caused it, or you have the same condition, it's probably worth asking your doctor.
Menopause is simply when your ovaries run out of eggs, and Boots and other chemists sell home-testing kits which are supposed to give you some indication of how much time you have left - I assume that they're based on proper medical kit, which maybe your doctor can refer you towards, as you have a real concern?
Good luck!