Am i being overly sensitive?

big family problem-ill be first to say that im sensitive. not to much but still. my mother has been in a bad mood all day. my brother (he is ten) will mock me and ill get mad and tell and he doesn't get in trouble. he will sit there calling me and idiot and jerk and a bunch of crap then i will tell him to shutup and he doesnt so instead of fighting ill go get mother to stop him yet she just says be th bigger person. he was playing a game on the computer and i plugged in my ipod to charge. it must have messed him up but he started yelling at me and i got yelled at. i am crying right now. then something will happen and i feel guilty. like my dog pooped in the middle of the floor and i accidently stepped in it...it got mushed into the carpet and i could tell she was upset and i started to feel horrible...like i said i am crying right now...there is really no one i can talk to yes i have friends but the only one i think i could even think abt talking to has her own problems that ofcourse i aint saying and also the only place i could talk to her is school .... what can i do?