Base Flood Elevation??

Just received notice from mortgage company that I need to add flood insurance. I am kind of confused on elevations. FEMA has my home at 3.8. 1984 plans of neighborhood have my elevation at 5.5. 2010 survey when purchased notes that elevation is over 5.0. What is an elevation certificate? What exactly is a LOMA? Can those two help with an exemption to the requirement? My neighbors are paying over $2400 a year for flood.