I need to release my feelings

I haven't felt this depressed since 6th grade...I'm in high school (17 now) and I've never been part of a clique or really any friend group. I used to have close friends in elementary school and I'd hang out with them sometimes throughout middle school but rarely in high school. I don't have any classes with my old best friends. I also don't have any social media or anything to keep me updated on things (1. I'm not allowed to have anything and 2. I wouldn't want it anyway) I see all of my old friends get together constantly and they never invite me. I've talked to them about excluding me and it doesn't get anywhere. I have acquaintances in my classes but no one actually considers me a friend enough to hang out with me. I'll ask people what they're doing on a certain day and if they're not busy so we can get together but there's always an excuse. I'm really starting to think there's something wrong with me. I make people laugh and they seem like they enjoy my presence in school but they're not my friend. I don't even know what a friend is. I see all these girls on twitter or Instagram or VSCO with pictures of them so happy with friends or just happy in selfies. I wish I felt like that. I envy everyone else. Everyone has jobs, friends, cars and everyone seems so happy with their lives. I had a job and got fired my an employee who said the boss said "it wasn't working out." A lot of people have their close friends from sports which I can't participate in because of a medical issue. Im in band... but the kids in my band have their own pre-made cliques dating back to elementary and middle school. I feel so alone when I hear friends cheering on their friends in my band when we perform when I have no one that even cares about the fact that I am in band. When I tell you that I NEVER leave my house besides school and occasional band events, I mean I never go out. My parents are mildly strict so it isn't like I can just say "I'm going out with my friends until (whenever) bye". They have to know a parent is going to be with us and know the kids and all that stuff. I'm just feeling so insecure. I'm graduating this year and I feel like I should be much happier and secure as a person. I'm not happy about myself at all. I feel like I have a constant cloud of guilt and insecurity over me 24/7 (sometimes I'm able to put the cloud away if I'm doing something that distracts my mind but it'll always come back). I just need to release this. Even though this is only a little of what's going on.