Extreme depression

Im 18 weeks pregnant and I find myself thinking about suicide a lot. I think I would have done it already if I wasn't pregnant, and I don't know why I'm so upset. I feel like I'm not going anywhere in life and that nothing will ever improve. Nobody has ever loved me or ever put me first. In my whole life drugs and alcohol have always been chosen before me, and I feel so lonely. I don't want my baby brought up in a world like that either, and I feel like I'll be a horrible parent. I am only feeling worse and worse all the time, nothing goes well for me anymore. I hate feeling like this and I know its not right but I feel so down, I don't feel angry, happy, or excited anymore. I just have a deep feeling of sadness and self hatred, like everything is my fault and the world would be so much better without me in it.