People used to guess higher when I spoke (I go out of my way to be intelligent and articulate) rather than just going by looks. Unfortunately there is something close to painful when people don't take you seriously because they think you are 17 or 18 when you are in fact 36.
We got so much shit trying to move sometime back because the realtors kept thinking I was barely of age AND stupid enough to think I could get out of the lease by pretending to be underage. I have a lot of trouble with vets because they don't actually listen (we barely found, now on our fourth, one who actually hears me out instead of dismissing me) because I don't look old enough to know jack shit or something. I had to stop wearing my favorite t-shirts (avengers, xenomorph anatomy, etc) because I get treated like a teen even if I wear makeup.
I have even tried dressing up and everything, makeup, etc. Nada. It's really getting old. I hope that the last 40-50lbs I have to lose for my health will make me look closer to my age. I wouldn't care if I looked 20 or something just not "not old enough for anything".