cows milk at 11 months??

Ashley • I'm 29 and my husband and I have been married since October 2014! We now have 2 children a 2 year old and a 5 month old. This app helped us get pregnant both times!
My son is 11 months on Friday. I just recently found out I'm pregnant again and am worried I'm drying up! I really don't want to give him formula this late in the game. Has anyone ever started cows milk around this time??