Sprint for 10 minutes each day.
Get enough vitamin D, it's used to absorb calcium
Go to the doctor and ask for steroids so you can grow
If you're shorter than you should be you can try getting human growth hormones from the doctor that should shoot you up to your parents height
If you have a fucked up back getting your spine fix with proper posture will make you taller
If you for some reason reached your maximum at 18 and can't cope either kill yourself or get leg extension surgery