The most likely cause for this is the scaling in blender. Either the armature, the scene settings, or the export settings.
It could also be the import settings in UE, but I doubt that.
- Blender for Unreal Engine might help you.
- Importing Characters from Blender to Unreal.
- The recent Blender to Unreal livestream.
Sorry, but unless you provide me with a ton of screenshots of your import and export settings, as well as your armature & animation properties, I can not be sure what is wrong.