My Grandson Is 16 Months Old. I Have Been Noticing

My grandson is 16 months old. I have been noticing more and more lately that he vomits after drinking his milk or juice. When he was an infant he was breastfed. When trying to switch him from breast to formula around 6 months, he rejected the formula. He drank the formula but when it was time to burp him, he vomited in a projectile manner. The pediatrician was informed and we were told that it was normal and to just keep giving it to him. After a week of this formula transition, the mother went back to feeding him breast milk only (for a month) and the projectile vomiting went away. When he was 8-9 months old, the mother began giving him Gerber Good Start and he seemed to be ok drinking that. When he turned one year, the mother switched him to whole milk per pediatrician. He began vomiting again. He had a healthy appetite for food since he was able to eat "table" food and that changed overnight. At 13 months, he began refusing to eat food. The pediatrician recommended giving PediaSure as a supplement. The Pedia Sure was the only thing he would drink and maybe a chicken nugget and a few no more than 5 french fries. This was very abnormal from the way he used to eat. He then began projectile vomiting the Pedia Sure too. At no point was he sick when the vomiting occurred. He is now 16 months old and is drinking Silk Soy Vanilla milk and that was going good at first but now he is projectile vomiting that too. When he drinks juice, (Juicy Juice) he occasionally vomits that. I did google to see what I could find and I seen something about Pyloric Stenosis and wondered if this could possibly be the issue, can you help me?