What should I do? (Stressed and Confused)?

Your exactly right! Your future is in your hands don't let these setbacks get you down. Your sternum is probably only bruised. Happened to me once before it hurt to cough laugh, and yes do push-ups. Relax and on your finals do all the ones you know off of the top of your head first, then the harder ones. The situation with your mother is in god's hands.LET GO & LET GOD. He will take care of it. Best Wishes.