Why does this always happen to me

My storys might not be as bad as some peoples on here but it is bad enough to make me cry myself to sleep sometimesmy mum and dad are divorced i used to wait for hours upon hours waiting to be picked up by my dad and sometimes he never came he didnt get in touch for weeks sometimes months he has changed a bit now as he is now paying benifts.but i have only started realising how much pain he has given my mother, another thing is he is 40 and he dates 25 year olds sometimes younger but he is now dating one with a kid and if he mistreats her there is a young child involved aswell.and lately me any mother havent stopped arguing me and my big brother have big and proper fist fights sometimes i wanna get away from it all.at school there is this lad who is 2 years older than me and he harrases me like feels me up and he brags about it to his mates and to me and he wont stop i have tried ignoring him but he always finds his way back around i have also tried telling a teacher too but they said that they couldnt do anything any advice?