I'm pregnant and severly depressed, very stressful time in my life...need help read on...?

Im 11 wks. I found out about a week or so ago that my boyfriend (the father) cheated on me in February, while I was on vacation with my mother..he said he was "really trashed" and would have never done this to me if he were sober. My doctor just took me off of my zoloft prescription, so I'm dealing with that as well. My mother is trying to control ever aspect of my pregnancy and I feel she may try and take custody of my child when it's born (I'm 19, she cant do that right?) And there is just a overwhelming feeling of insecurity and stress that I am going to be left alone, forever.....It's just so powerful...I'm having suicidal thoughts of killing myself after the baby is born...this is all just really stressful and I know it seems like I'm whining but I really need help...advice or something