My fathers grandmother, and my mothers mother, both had breast cancer, i am 40, should i be worried. does it skip generations or is it off mom or dads?

Cancer lot of factor: Developing breast cancer is not just genetic there are lots of factors. But yes if there is a strong family history a person should be concerned. It depends on when your relatives had breast cancer. If many had breast cancer in their 40-50's then there should be some concern. Genetic Breast cancer can come from mom or dads side, due to autosomal dominant nature, difficult to tell regarding skip.