Are you male or female? I can be sympathetic as I've known people that tall of both sexes but the problems for each sex are different as well as what is the norm.
hi , being only 5.1 myself i feel i can be honest ! it aint that bad and you could still grow a little i myself prefer small men and married a 5.3 man and wouldnt have it any other way . they canot give you anything unless it was proven to be a hormone problem .x x
At 18 chances are even if it's hormonal very little could be done. Most of the long bones will have calcified.
the growth plates in the long bones usually calcify sooner in girls than in boys. Get an x-ray of your left rist to be sure they have closed, its not that unusual, especially boys, to grow at 18+ years old. There's even reports of mature women growing an inch or 2 after pregnancy