What type of internships are you looking for, i.e. what field do you want to go into in the future? This could be nursing, teaching, engineering, business, etc. Knowing what field you're interested in would be helpful to determine next steps for you, and how to prepare for your future without an internship.
In Pennsylvania, I found the below two resources for internships:
There aren't many companies I know of that are looking for interns who are in high school, but the internet is a great resource for you to look. If you are unable to find an internship, look for volunteer opportunities that are related to your chosen field. This is a great way to pad your resume, even when you can't find an internship. It shows you're interested in the field and willing to get any knowledge and experience you can.
Work hard, have a positive attitude, and you will be successful!