Talk with your guidance counselor at school and ask him or her to help you to prepare a good academic schedule that will help you get into a good college...your education is the key to your future success. Work hard at your school studies but, remember to schedule some downtime for "fun."
In addition, join extracurricular activities that interest you... even if you are afraid of social interactions. Everybody is afraid in new situations but, over time, you will become less afraid and may just find that one 'true" friend that will remain a friend for life. Do some VOLUNTEER work in your community...at an animal shelter, playground, hospital, etc as these kinds of activities look good on a college application and future job applications as well.
Use your time productively.
Best of luck to you!