Heat oven to 350 degrees and line 2 standard-sized muffin pans with paper liners. In a large bowl, stir together flour, oats, brown sugar, flaxseed, baking soda, baking powder and cinnamon. Add eggs, oil, buttermilk and 3/4 cup water. Mix until dry and wet ingredients are just combined. Fold in blueberries. Spoon the batter into the muffin cups, filling each cup right up to the top. Bake for 20-25 minutes, until toothpick inserted into the center comes out clean. Cool in pan for 5 minutes, then turn out onto rack and cool completely before serving.