school ig

okay so I was gone for like three days due to breaking my thumb and being sick. I wound up with 13 missing and I cant keep up with all the work, I kinda need some advice. I'm able to go to the recourse room to work but there's always some fuckass sped kids in there yelling and screaming. i can never focus with this one friend (I don't like her.) always talking and being like "gyat!" like SHUT THE FUCK UP BEFORE I SLIT YOUR THROAT. anyways, I don't know how to tell her to shut up without her going "no you" like bitch, SHUT THE FUCK UP. I just need some help with everything, my mental healths going down against and I'm almost 2 months clean of self harm but I'm so fucking tempted to ruin it. I'm currently in swimming in school so I cant hurt myself with fear of the teacher telling my parents. I'm grounded because of my grades (D, D, F, C, C and a B.) the one class I'm failing is math and since I'm gonna so much I don't understand what were doing in there. I struggle with  multiple mental disorders, one being extreme social anxiety. I also have a phobia of leaving the house. I'm so god damn clingy its killing me. I get too attached to everyone around me and I just end up hurting myself. My boyfriend left me like almost two months ago and I'm still thinking about it. My mom doesn't even know I have this and what's worse is its making me guilty of having it and I don't know why. I feel like my life's just falling apart. I don't think I'm going to make it to 18, I stopped eating a few days ago.