17 and now, Pregnant

Hey ladies. Need your stories-advice.
When I was 15 I didn't know I was pregnant and miscarried at 12 weeks. Living away from home, I went through it alone and have cried every night because of the guilt I felt. I had been smoking and drinking because I was dealing with suicidal thoughts brought on by a terrible breakup and alienation in school. 
I started seeing a guy who's been my best friend for years and I have just now literally come back from the doctor who told me my late period and nausea was because I was about 4 weeks pregnant.
I my past pregnancy, my maternal instincts heightened, and I know I want this baby, more than anything, but I don't know what to do. 
Please share your stories or any tips you may have to help a girl out.