HELP 10 pts what wrong with me?!?

Okay so I'm 11 and I got lots of problems to explain. So I am very stressed. Another is I'm very slim. I'm only 75.2 lbs. How do I get heavier? And one last thing I got hit in the stomach yesterday with a soccer ball. Now when I make a mussel, my tummy hurts. HELP! IM SO STRESSED PLZ ANSWER ALL OF THESE THREE THINGS PLZ!!!