Family problems? Please help me?

So heres the story i am a teenage girl and my parents divorced when i was 6 since then we have been living happily most of the time. My mom is always flirting with people and talking to many guys at the same time, well she found this guy that she likes but i hate him. My mom never cares about me since i am the middle child, i think that with a guy around i wont even be noticed. This guy has money and is kind to her. My mom wanted career over children before i was born so i dont think she likes having children to look after. This guy comes over alot and everytime he does we get into a fight. He dosent seem as nice as everyone thinks. My mom is always lying about seeing him. Recently she lied to me saying that her work was taking her to paris for a week but it turned out that she was going with him. My mom barrly acts like a mum and i absolutly despise this guy he always is rude to me and if they get married i dont want him to be my father. I tried telling my mom she dosent care. I know that i am selfish and i want to make this relationship work but its so hard when i really hate this guy! How can i make this work and be happy for my mom when i cant even stop fighting? How can i stop fighting? It hurts to see them together and because of him my mom is always lying to me. help me cope with this? Please? Oh and i cant move out im too yound and i cant contact my father. Help!?