I'm going to be completely honest here because you sound exactly like me. I'm also from Illinois, I'm 27 now and back when I was 15 I came home from school, ignored my work, played video games, etc. Never took pills. I aced every test I ever took. I failed 8th grade and had to re-take the whole year. I dropped out after 10th grade when I saw an easy way out. The main difference is that mine was mostly due to anxiety but as a result I was extremely lazy.
I still am. There are two paths you can take I think that would help you in the long run. You can either:
A. Suck it up. Trust me, I have heard no end to the amount of people saying "Just do it" "It's in your head" "What's wrong with you?" It's the WAY wrong way to deal with it but to get through what you're going through you will have to dig deep and be who you are. That youtube video isn't going to help you when you're 27 in a minimum wage job and you have to worry about whether or not you can afford food tonight.
B. (This is my current goal, however it took me many more years to figure this out) Find something you love and just go for it. I dropped out of school when I saw an easy way out. I made excuse after excuse as to why I couldn't do something. Can't afford school. Can't get a better job cause I haven't gone to school. Can't go out tonight with friends because I have this thing I need to do but the thing I need to do is really just laying in bed feeling sorry for myself because everyone I know is successful and happy beyond my wildest dreams. That's not right. You deserve every happiness in this world. The first step here is finding something you WILL get out of bed for. You WILL get off your computer to go work on. It took me a long time but developing video games is something I have an extreme passion for, so that's what I am working towards now.
Lastly, you need to stop being in denial. You very much are depressed. Depression isn't just about being sad. Depression is a mood disorder that makes people feel sad OR have a loss of interest. We are in the same boat man. I spent 3 years of my life inside my bedroom. Literally. I had a bathroom connected to my bedroom and from the ages of 17 to 20 I did not go anywhere besides those two rooms. My mom brought me all my food, I had internet, I was good. I thought I was content, but looking back it was the period in my life where I was most lonely.
TL;DR - Find something that makes you want to not be lazy, focus on that. Your parents (if they are reasonable) will note your increased focus and as a byproduct of you falling in love with something, the increased focus will help you in your day to day life.