Desperately in need answers, feeling like i don't matter?

lately for the past four months i have been feeling depressed, resentful, numb...things i don't usually feel for extended periods of time. keep in mind i had a concussion before this. i've been locking myself in my room to try and keep my negativity away from my family because they have enough problems without mine mixed in. (i'm also trying to do what i like, reading and writing, like everyone keeps telling me to to manage my emotions but its not quite working for me) i feel hopeless and on edge constantly and i don't care about my grades in school anymore, i feel constantly weak and depressed and i don't know what to do. though its humiliating for me to admit,self mutilation and suicide have crossed my mind many times but i've never acted on them. i feel like what i say doesn't matter and my words are just dismissed whenever i try to talk to anyone about these problems. i've gone to my mom to try and get her to let me see a professional but she thinks im just making it up and i'm doing this to myself. her exact words are if i keep thinking i have a problem then i eventually believe i do, but that's not it, i let things go pretty quickly but they always lurk in the back of my mind and come back when im at my weakest and they've just kept building and building and now its just turned me into this person i don't recognize anymore, because of this i became moody and irritable and the things i used to love to do now i can't even bring myself to do. i force myself to hang around my loved ones because they always talk about how i always avoid them and hate hanging out with them, which isn't the case. i feel like no one cares how i feel and it isn't letting up the way everyone keeps telling me it will. i feel like i shouldn't even be feeling this way sometimes because i'm not like other people who feel depressed (i haven't lost any loved ones, been abused, or have a split up family or anything like that but my life isn't perfect either...) but i do feel like my life i being controlled constantly, i'm told all the time what i should do and what my future will be and i get no say in how my life will be like. (i'm going to collage whither i like it or not, i'm not allowed to get under a 85 in any of my classes, etc) the suicidal thoughts are now more frequent and im scared that one day ill act on it, what should i do? please i need answers right away