Is it normal if i feel like i'm getting younger?

I dont get it. I feel like Im getting younger as I get older in terms of looks and how I come off. My voice sounds lighter, my body looks smaller like it hasn't gone through puberty, and overall just my appearance. In terms of how I carry myself, I have been told Im mature which yeah cause I am older and more mature than they think I am. But its honestly beginning to get frustrating because I feel as if it's getting in my way of being taken seriously. People look down on me or underestimate me when no I have been through more than you think. But I feel as if I can't convince them because of how I appear. Like i said my voice sounds so light, like a little girl. Not sure how to portray myself older. I want to look older. Sometimes I think I look older then someone says are you still in high school? Im like no!