A very good student in physics and math can certainly have a good shot at a career in astronomy! I was a solid B+ average student in high school who worked real hard to get the very few A's I got in math and physics each marking period. It wasn't until college that I really found my stride and all that math and physics finally made sense! There is hope for you still. Just hang in there.
About living at home, however, there is a good probability you will have to live with your folks the rest of your life. Enjoy it as long as you can.