Please i need ase many answers ase i can possibly get im so worried about this?

im 27weeks pregnant and i gave to go get a level 3 ultrasound i don't know what they do if i get pic or if anyone can go back with me and im so scared that thel find something wrong i never thought their was besides i meur a little small and im a tad bit low on amniotic fluid even though im still on the normal side of it when they called to tell me i needed it they didn't mack it sound urgent they just said he may not be growing rite and they needed a better look the only problem i even remember them having during the whole ultrasound was he was being stubborn and wouldn't turn his head so she could see his face im so scared that iv done something wrong to cause this so i want to know what kind of things they look for because the only thing i have found out they look for was down syndrome but im 16 and not old (where most risks are at)so do they test for anything els im so scared please help me by answering this