Are you hitting with the right part of your shin consistently? you should be hitting on the the top 4-6 inches of your shin that is a little flat below your knee? Also make sure you are turning your hip over.
If the answer is yes continue with your bag at home. If the answer is no, quit the home training for awhile and spend some time with an instructor or experienced students to fix your technique. If you don't do this and continue to work out at home, you will end up developing bad habits that will need to be fixed later.
My .02 cents.