Placenta isn't working properly

Has anyone else gone thru this? My baby is measuring 2 weeks behind. Very small. My placenta isn't giving her the nutrients she needs. I'm supposed to be 21w but she's measuring 19w. I also have low amniotic fluid. I have to go back in 2 weeks and see if she grows if not I have to be put on medication and if that doesn't work, I have to deliver her super early :(
Has anyone else gone thru this? My doctor said there's a chance that this won't end well :( I'm just trying to get some support and advice. I'm trying to stay optimistic and strong for my little girl but this is hard. This is the worst thing that's ever happened to me