Dear Emily,
You're often ill,it's necesarry for you to do following things to be more healthy.
First of all,you should take more exercise,for a example,you can play sports like basketball,or you can run or swim.
Next,you should eat healthy food and have more fruit and vegetables.On the other hand,you also should drink more milk and water.And don't forget to get enough sleep.
Finally,I hope you can also stay happy.
Good luck!
Yours,
XXX.