Elevated AFP results

Got my AFP screening back showing 1:2 for open neural tube defect. I go the 24th for my anatomy scan (hope they can see something or better yet, not see anything) and I go the 29th for a level 2 ultrasound and more blood work..

Anybody else have this, what was the outcome. I also did research on why afp could be elevated and I can only guess one other factor beside baby having a defect and that's my gastational age is off. According to my last LMP I should be going on 20wks, but doctor says from ultrasound I'm only going on 18wks..

Need help. Please. Anyone...