As you are 18 year old, You are in approximate height .
As ur fathers height is around 5ft and mothers height is around 4ft ..u r likely to be in 5ft as per your genetic structure.
this is Quite Normal as per your age
1)Regular Jogging in early morning for 15 to 30 mins
2)Nutritional factors plays key role.. so check for Haemoglobin
3)Healthy food stuffs including Fruits intake
4)Increase your water intake.