Life Problems //Advice, Help PLEASE?

Hi everyone ! Firs thank you for giving a try to help me :)

Okay so I'm 17 years old. When I was 9 months my mom and dad get divorce. I start living my life with my dad, when I was 2 my mom got married, and when i was 4 my dad got married. I start seeing my mom when i start going to first grade, I never really cared about her, or maybe i just thought i didn't. when I turned 16 i moved to live with my mom in US so i moved from Europe. I didn't wan't to but i really have to because my dad is poor he doesn't have a lot of money and i got 2 step sisters and i have to take care of them i really love them. When i moved I didn't spoke English at all, for one year i learned a lot, everyone at school is proud of me, they really love. I start working and costumers are in love with me, but i never can make my mom happy. I'am really depressed :( Okay so I got 1 step brother ans 1 step sister they are younger than me, and my mom she is really nice with them so are with my step dad she always smiles with them and stuff. OMG i swear I'm really upset and i drop all my classes at school I use to have all A and right now they are B, C and my English teacher asked me what is wrong with me and i just start crying that was so bad cuz i never cry in front of people. She was trying to make me feel better and stuff, i told her she said talk to your mom, and i did today but my mom things that she is all right and i said to her if you are not happy with me i can go back, and she said if you want to i will tell your step dad to buy you a ticket and i said if i wanna go i can buy it by myself. I wanna kill myself but when i thing about my sisters and grandma i can't , but i really love my mom and i need that love back, cuz i missed her soo much. I don't believe in my self anymore, not for college i feel so dumb, If i go back there is no a good future for me, for my sisters If this is over my life is over too. Thank you !