I m 18 years old i take proper diet and also i doo...

usually the height stop growing after the age of 18 and the hieht of every one is determined by genetics

How to increase your height?

the cause of low height may be due to deformity in the spinal cord which can be treated according to its severity so in mild cases it can be treated by physical theraby and in severe cases surgery may be done other possible cause of low height is deficiency of growth hormone which if present then can be treated by growth hormone replacement under doctor supervision

How to diagnose  low height?

you should be assessed by the physician and has x ray done to the spine to exclude the presence of deformity in the spine and you can has level of insulin like growth factor test done to exclude the presence of low growth hormone level

what are the causes of low height?

genetic causes
spine deformity
low growth hormone

advice

you should follow up with the physician and has the lab test done