Why help others when they ingor you?

I’ve had enough with my life now, with the past three years being hellish for me as I have experienced bullying for no reason other then being me, lost many of my friends because I stood up for myself when no one else would and lost my best friends due to love. Having a stutter doesn’t make life easy but instead singles you out as a target for bullies and being shy and not telling anyone of the bullying it ends up going unnoticed but in feb 2013 one person was being ageessive towards me while playing football as he kept punching me in the back and kicking my ankles so I flipped and went ape shit at him I just kept flooring him and I had no control of my actions the only reason I stopped was when some people dragged him away from me,from then on people started to avoid me and started to hate and spread gossips about me. I ignored this but later that year I was diagnosed with dyslexia and people started making comments about how unfair it was for my extra time/help just because I am mucked up in the head, I admit I am not the smartest person but nearly scrape B’s. But the worse thing about it is all the teachers treat me differently as some will avoid me at all costs with one not talking to me for a month, but nothing could compear with what one teacher did. He forced me up to the front of the class and made me do this one minute non stop talk about a new topic, I told him I was uncomfortable with it but he was still making me do it. I only lasted 10 seconds and he saw livid and started to rant at me saying it was easy to talk in front of 15 people , I struggle talking to one person so I lost it I screamed so shit at him and walked out, went to an empty classroom and tried to find something to cut my self with. After this event I have said a grand total of 10 words to that teacher in 3 months and will most likely fail the course. Talking about how shit my school is they don’t give too shits about me or my feelings as long as I pass muy exams thy deem me ok with my best friend telling them about my suicidal thoughts 3 years ago and not checking up on me at all I given up with school life with my friends not helping much. With one of my best friends faye only helping me when it suites her but when she needs help I am always there, she always makes up some excuse like I was revising or my phone was out of charge but these are all lies as I have asked other friends and they talk to her when she is “revising” and David is eathier busy with music as he is really talented or with his girlfriend and leaving me alone to deal with this depression I have had since I was 13.I have now released that most people only use me for help but when I need it the ignored me. To cope with it I started cutting but I keep having memories of bad times replayed in my head every night and pains all over my body with shivers flowing down my body at random time even at 20°+. Tbh I have thought of killing myself in many ways but I don’t know the best way I am split between overdosing and jumping under a train I just need a break from this shit as I spend day to day cheering up others and helping people who do not give a dame about me.I give up.