OP, I suggest a bit of facial hair if you can grow it. Nothing big or weird - maybe even just a mustache. Facial hair usually makes a man look a bit older. And that might be part of the issue… If you need an inch or so height try cowboy or motorcycle boots. They add an inch or more… I also suggest looking at how the men around your age dress and compare your usual dress to that. It might be a more age appropriate wardrobe could help… Funny thing, when we’re young we’re in a hurry to be older. But when you’re old you wish you had some of that youth back.

if only you were bi.. lots of guys like the young / twink look

just focus on yourself and build a career. don't worry too much about girls. they will come around during the road