Single because I look to young ? :(

So, I'm a very mature 20 year old girl but I look super young.  (15 or 16; sometimes younger) Looking young is just something that runs in my family but I really hate it at this point of my life because people treat me as if I'm "young and stupid " (especially at work) and I feel like guys my age don't give me a chance because they think I'm super young because of my looks. How can I get over this? I know I should be grateful because "when I have kids I'll look young" but I feel like I can't even get a guy my age to give me a chance because of my young look. It's pretty much a curse and a blessing at the same time. I feel as if I'll be single forever. 😰 Help any advice or suggestions would be great. Anything I can do to appear older and more my age? 
P.s- I don't wear a lot of makeup (just mascara, eye liner and little blush once and a while) and I dress my age.