Is the lip filler very noticeable?

My upper lip is so thin that I look a bit fussy when I'm not doing anything. My lip skin has always been on the thinner side since I was young, but lately, when I keep my mouth closed, my upper lip curls inward, making it look like just a single, straight line. Because my lips lack volume, I often hear that I look petty and cold. No matter how carefully I apply lipstick, it doesn't create any dimension, so I've completely lost the joy of doing my makeup. Even when I try lip plumpers, they only sting for a moment without adding any fullness at all, so I'm wondering if I should get fillers to add a little thickness. I really don't want them to stick out unnaturally like a duck's; I just want to add fullness to the thinness right along my natural lip line. Is this possible?