In this counseling answer:
“Around 9 months old, the baby will be willing to either transition to a bottle, or, like my first baby, just start using a cup. When the baby gets a few teeth, you can put some soft cooked broccoli, or vegetables, or other healthy food chopped up into small bites on his/her plate. The baby can start learning how to chew solid foods.”
First, I must explain to you that I am not a medical doctor, or a nutritionist, or a pediatrician. I will speak only from my own experience as a mother. Also, there are many different schools of thought on this, I am just speaking as a mother and letting you know my own personal preference.
If you can breastfeed, do this until the baby is between 9 months and 15 months old. But in addition to the breastfeeding, you can start to slowly introduce soft solids, puréed vegetables and meats. Introduce this very slowly so that the stomach has an opportunity to learn how to digest the solid food. Increase the amount from one ounce to one and ½ ounce the next week and so on until your baby is eating three “meals” a day.
At around 4 to 6 months, baby can usually tolerate some puréed oatmeal or cream of wheat. When they start to eat solids, they drink less milk. Although I prefer breastfeeding, because it really helps with the immune system, at the age of three months, you can start giving a little formula. This will help the baby acquire a taste for it.
Around 9 months old, the baby will be willing to either transition to a bottle, or, like my first baby, just start using a cup. When the baby gets a few teeth, you can put some soft cooked broccoli, or vegetables, or other healthy food chopped up into small bites on his/her plate. The baby can start learning how to chew solid foods.
At the beginning, this will be a big mess and not much will actually get into baby’s mouth, but eventually, if you find a soft food that he/she really likes, the baby will start to learn how to eat. Supplement with the puréed baby food and formula so that baby is getting enough protein. As your baby gets more teeth, and the ability to pinch fingers together develops, you can start to put a small bite of cereal on her/his plate.
By the time the baby is a year old, you will probably not be puréeing much, and the amount of breast milk or formula that baby wants will have decreased as you will be increasing the amount of tiny bites of solid food that baby gets. The transition from formula or breast milk to regular milk should be slow. Just start to introduce the whole milk into the formula or breast milk a little at a time so that the stomach gets used to it and also the baby acquires a taste for it.
By 2 years old, the baby will be eating solid food, cut up into small bites, using his/her fingers to eat finger food, and drinking milk. Some children are allergic to milk and are lactose intolerant, so if you find that milk is giving your baby a stomach ache, try to get your baby to drink soy milk or rice milk instead.
Check out this counseling video:
I hope this information is helpful for you. Is your wife helping you with the baby? Is this your baby?
Disclaimer: The conceptualization and recommendations stated in this response are very general and purely based on the limited information that was provided in the question. You are strongly advised to seek face-to-face counseling and consult your physician or therapist when making a drastic change in your lifestyle in terms of behavior, medication or diet etc.