What do you suggest if i am 16 5'2 in height i was premature as a baby, i was like 4'5 at 6 and barely grew since then. height by age 21 at least?

That's a difficult..: ..question to answer and depends on lots of different factors, like your parents' heights, your growth curve to-date, pubertal stage, etc. If your height bothers you, you're worried about it, or it's affecting your self-esteem or self-image, then you should see your pediatrician about it. They can give you a better estimate of your height potential and what might or might not be done about it.