Hello /r/seduction, I need some advice on how to re-obtain friends/ pick up chicks how I used to.

I'm currently a junior in high school and was under home instruction for a third of my freshman year and all of my sophomore year because of kidney stones/ pancreas problems. I'm here because I need your help, I've changed a lot since my freshman year and I don't really like the changes. My freshman year I was extremely confident, I was one of 'the guys', I went to parties, had a ton of friends and could pretty much hook up with any chick I wanted. When I started home instruction I stopped using ANY social media and pretty much dissociated my self with everybody. I literally did nothing but play video games my sophomore year and talk to my 'online friends'. This year (my junior year) many of my old friends just completely ignore me, in my past years I felt like I had a voice, people would listen to what I would say. I am no longer confident, I don't go to any parties, I have a very small friend circle (20-30) and I don't enjoy this. I also pretty much talk to almost no girls because of my lack of confidence even though I know I'm a solid 8/10...

I want to be who I was when I was a freshman, how do I re-obtain my confidence. How do I get people to like me again?

Forgot to mention my change in personality if that helps with anything. My freshman year I felt alive? I was that guy who could always make you laugh. I could literally start a conversation with anybody whenever I wanted to. Now I have a more sarcastic sense of humor which people don't seem to pick up a lot. I am extremely quiet in most of my classes and I feel really awkward just sitting there and listening to people talk and just chuckling whenever something funny comes up and I can't help it because I feel like I have nothing to say.

I've been told that I seem more mature than my previous years by some of my teachers and other people, but is that really it? Am I just being 'mature'?