Please listen to me. 3 years ago our granddaughter had the same problem. She was exactly the same as your son they are allergic to the formula. Our son tried every formula on the market. The poor baby was bleeding in her stools.
After nothing else worked for them they listened to me. My husband grew up with a boy who was alergic to milk. His mom raised him on goats milk.
Walmart sells it in 16 0z. cans about $1.50 a can.
Mix it half and half with water and feed it to her instead of formula.
Our son and his wife got her the milk and within a day she was doing better. After about a week she was fine and acting like a newborn should.
A year and a half later when their second girl was born she was the same way. needless to say they did not wait to give her the goats milk.
Please save yourself a lot of grief and the baby further pain and get some goats milk today.
Feel free to email us if you have any questions.
Kathy