It's nothing to freak out about yet girl. TRY not to stress! I know it's SO hard. My kiddo was diagnosed with the same thing when I was pregnant and I panicked. Like almost called off his babyshower cause I thought somethin horrible was gonna happen. They will just start monitoring you more often, more ultrasounds and checkin up on babe a LOT more often. It just means he's not growing as fast as they'd like. In my case, it was just because I'm a pretty small framed person and he just didn't have the room. We went to weekly ultrasounds with the worry of a possible early delivery. They'll just watch you guys and if it gets to a point that baby just can't grow inside anymore, they'll induce you. Their goal, OF COURSE, is to get you as close to full term as they can without presenting a danger to baby or Mama. It's just gonna take time to monitor. TRY to relax and just take it an ultrasound at a time girl. Also ask ALL and ANY questions that come to your mind when your in a check up.
The plus is you'll get 3D ultrasounds like bi-weekly for a couple-few months. I always LOVED gettin to see the baby!