My upper lip curls inward and is thin, so I am considering fillers. Will the volume be added naturally?

Ever since I was young, my lips have been naturally very thin and lack volume. When I keep my mouth closed, my upper lip curls inward, making me look petty and picky. In particular, whenever I apply lipstick, no matter how wide I apply the line to create an over-lip, it lacks dimension and just sits on the surface. My lip corners also droop, so when I'm just standing still, I'm often mistaken for someone who is angry. Even though I apply lip plumpers every day, they only provide a brief stinging sensation and swelling, so I am considering lip fillers to create lasting fullness and a defined lip line. I am cautious because I worry about side effects, such as my lips protruding excessively like a duck's beak or feeling lumps of foreign material. I would like to hear tips from those who, like me, have gotten lip fillers for thin and flat lips and achieved just the right amount of volume and a natural lip shape.