Bless your heart, it looks like you've had more than your fair share. However, the fact that you have not walked away from this responsibility, which you seem to have inherited, says quite a lot about your character.
Caregiving is the most demanding job in the world, both physically and emotionally. You may very well benefit from a caregiver support group. I am going to provide the following link which has excellent tips and also a link where you can join a support group.
By the way, do I understand that you are doing this all by yourself? Your husband needs to help you and you need to have special time for yourself and special time for you and hubby.