Every body has a predetermined height coded into their genes. There is no way a person can grow beyond that limit. However there are numerous factors which prevent one from reaching his/her optimal height. Common reasons are poor nutrition, low
vitamin intake, chronic illness etc.
You are only 18yrs old so you still have a few years of growth left.
Next Steps
Consult a nutritionist. Go to gym and begin exercise. Take
vitamin supplements.
Health Tips
When you grow old you will realise that it's more important to get a healthy body than a tall body. People love you for who you are not for what type of body you have.