I really feel for you in the situation you are in. 17, pregnant and having trouble at home! When I was 17, I didn't get on with my parents, always rowing and telling them I was going to leave....I managed to move out when I was 19 and I can tell you, it was really tough....And I didn't have a baby to think about.
If I could offer you some advice I would advise that you talk to someone, a support line, teenage support service (do you have samaritans over in the us, or childline or social services).
You are going to be going through the hardest time in your life...Although I am in the process of ttc, I know that when, (if) things happen, I will need all the support I can get, and I know that I will be leaning on my mum to help me through the first few months.
You are so young, your hormones are in termoil not only being pregnant, but because of your age. I was very suicidal when I was 17 and continued to be unsettled until I was about 25. Try stepping back from the situation and understand why your mum is being the way she is. Perhaps, she is worried that you won't cope, or she won't be able to cope with her baby having a baby.
I hope that you get the proper support that you need. Keep posting and let us know what happens.
Good luck.