what mental illness do I have?

[Kiwimouse Emily]

hi. i am a 13 year old girl, my name is emily. i am a very sad person. my family and friends are wonderful, loving people. it isn't them, it is me. i cry constantly at least once a day. i seem to have episodes of this. the last one i had was 1 month ago. my grades started slipping, so i was stressed. i went from a straight a student, to a c and d student. i lost my appetite and i dropped 6 or 7 lbs. i atte.pted suicide twice, once with scissors once with a knife. i was irritable with my little brother. but my sadness went mainly with myself. i felt lifeless, more dead then alive. i wanted to die. anyways, i had told my mom a lot about it. she has depression and like 2 months ago, my great uncle shot himself. my mom said she was really worried about the suicide attempts and i won't go in to detail. anyways, that wad the time before now. now, i have exams coming up so i am stressed out. whenever i get in trouble or hurt myself on accident, i feel like satan is punishing me (i am a christian). i feel like he wants to drag me into hell where i belong. i cut myself, and i rake my fingernails on my legs and arms when i am upset with myself. often, i have to go to the bathroom during 6th period, chorus. most of our school is outside, so when i go outside to walk to the bathroom, i hear normal things, wind, the custodian with the trash cans, and thats pretty much it. but a lot of times, i hear a voice that i believe to be satan dragging me into hell. i hear myslef screaming and satans voice. it absolutely terrifies me. i feel like satan is watching me 24/7. i am too terrified to tell anyone. not even my mom whom i am so close to. i feel lifeless, dead. i want to tell someone, my mom, oh so badly. but i am afraid because it probably sounds stupid. "satan wants to drag me to hell" :'(. my mom would probably tell my dad and they would take me to a psychiatrist or something and it would be the most embarassing thing. people at school would know too. although i am very quiet. please, i beg of you, advice.
very nice answer samantha, thank you, you just might get 10 points!