Please please help me, I need help!?

My parents got divorced when I was 6. My mom has had her "friend"(boy) come over almost every week. I have a bad vibe with him, idk why. But I have been bottling up my feelings every since then, i always want to just cry when he comes over. My mom will get mad at him and he'll just ignore her or blow it of. But my dad knew how to handle it perfectly. I can't take it anymore, it's killing me! I can't hold in my tears or anything! I dont like him not one bit!! My mom has been so involved with him, she dosent have any time for me or my sister, and when she does, oh, its with him. Sometimes it makes me want to die. I think, its my fault though. My parents and sister were perfectly fine without me. But as long as I can remember, after I was born they always started fighting. They're probably better off without me anyways. I've seen pictures of them, before me, and they always looked happy. I think, i was a accident. Sometimes I want to just die, never have been born. What, wat do I do, i dont want to screw up their lifes anymore, but im going to die if I keep acting like everythings okay, and its not.