Social anxiety and high school, not sure if i can do it?

so I'm 15 and in 9th grade and in the middle of 8th grade i left my school to do online schooling. i had missed quite a bit of school before then from grade 1-8 because of my anxiety, social anxiety, and depression. so in the middle of 8th grade i got swine flue and no one really believed me, and some one had told me, my anxiety got so bad about thinking all these people we're talking about me so i started online. so this year around Christmas i kind of had a break down (bad depression, couldnt eat, had panic attack, crying all the time, etc.) and realized my public highschool would be in my best interest, so i decided i needed to transfer.the problem is i'm going back in a few day or a week and i'm really scared to see these people again, and dont know what to say if they ask why i left or confront me. oh also i only told and stayed in touch with one person from that school. and i'm just very terrified to go to the high school, any help would be greatly appreciated :).... also should i go this monday or next. cause i want to make friends soon as i really have none since i left my middle school and my birthday is in july and i dont want to have another crappy birthday with just family. especially on my 16th.