How can I stop feeling so depressed ?

Beginning of freshman year I had lots of friends and a pretty good life . In one of my cles I started talking to this girl , we soon became bestfriends only problem is she had a totally different lifestyle than i did. She grew up in a family of drugs and abuse - my family was nothing like that. I started doing drugs with her all my other friends found out so I lost them. I thought nothing of it cause i thought my new friend was the coolest friend ever. I never was a trouble maker now all the sudden I was. My mom found out about her and what she and i were up to and banned me from hanging with her. That didn't stop me from seeing her though I would lie all the time to my mom about hanging with someone else but i was reallly with her. Sophmore year came and we were still bestfriends . Few weeks after school started I had gotten introuble with law .. Which did it for me and made me realize how dumb i really looked. I had spent all freshman year grounded along with about half sophmore year grounded. My grades were **** i was lucky if I ped with d's . I met this girl in English we became decent friends she was a positve person to. Although I was still friends with the bad influence. I balanced off the both of them even though them two despised eachother. At the end of sophmore year I started my first serious relationship with a guy. He was perfect, and still is. He's the only bestfriend i have right now. Only problem is he goes to a different school about 20 mins away. So I don't get to see him as much as I'd like to. He changed me on so many good ways and I finally dropped her as friend. I spent all of summmer hanging with my boyfriend and somewhat with the positive girl I met but not like a bestfriend. Junior year just started 2 weeks ago for me and i have never felt so alone or depressed in my life. I've never had the problem with making new friends and I've never had a time where I've had lk no friends at all. I never just go out wih a group of "girlfriends" and I never have sleepovers or anything. It really depresses me I feel lk a major loner. I have no friends because people have heard so much about me and it sucks I wish I could go back and change it but I know I can't. I feel like a total failure at life sometimes I feel like I'm no good to anyone and that I should just cut off my life. I feel like switching should but i doubt my mom will let me. Idk what to do someone please help and make me feel like there's hope cause I'm close to giving up .