Ever since we had a new baby my 3 year old has become more aggressive, especially towards me. I have read this is normal, but for how long?

My 2 year old son only drinks 1 glass of milk a day. I am worried he is not getting enough.The American Academy of Pediatrics recently increased their recommendations for the amount of daily Vitamin D to 400 IU/d. Milk products are an easy source of Vitamin D as well as calcium and protein.

I have a one month old and am concerned about the flu. What can I do?