How can I feel more confident (for teenage girl)?

I have never really had high self-esteem. I was 4'8" and weighed 145 lbs. in the 6th grade and had barely any friends because I had moved in the middle of the year to a new middle school. I used to come home balling everyday. Plus I have ADHD so I was never good with friends because I don't know when to shut up. Summer going into 7th I got my first period and I dropped 30 lbs., so I felt a little better about myself. Then I got full B's in the 8th grade (which was very uncommon in my middle school) and I was definitely a lot prettier. Freshman year was a blast, I felt like I could have whatever boy I wanted whenever I wanted him! I started having so I wanted to try the depo provera shot (despite all the warnings about weight gain). After me and the guy had a fallout, I started gaining lots of weight. I went from 130 to 145 lbs. A hair dresser messed up my hair and cut my hair up past my chin and I just felt so hideous. Especially since all my friends I went to the beach with had a fear of weighing in the triple digits. After the 3 months of the shot, I stopped getting my period for 5 months AFTER those 3 months and gained even more weight. I just got it back last Saturday. I now weigh 150 lbs. and I'm 5'3". I look and feel awful. I just feel horrible. All my friends fit into 1, 3, or 5 and I can't even fit into a 7!!! Getting my period back gave me hope that some of the weight might go away again, but I'm out of hope! I just want to feel happy and have confidence again! You have NO idea what it's like to feel uncomfortable in your own skin and walk around and just say to yourself "I hope they don't make fun of me." or "I hope they just ignore me.". I cry all the time and I just want to fit in and stop being such a spazz. Does anyone have any advice that doesn't involve "standing in front of a mirror naked and saying "I love myself""? Because that is not going to work (I can't bare to look at myself in a mirror WITH my clothes on). I want to feel pretty again and not so uncomfortable in public. PLEASE HELP!!! :(