Hello. I'm sorry this is going on. I'm sure it is scary as the mom of a newborn! You've been to the doctors and no one on the internet can override what doctors say or diagnose. If you are unsure, don't believe them, think they are wrong-- how about calling a different doctor? Or continuing to contact your current doctor? There is an old phrase -- squeaky wheel gets the oil. Basically, this means that you need to be loud, and continue to contact them, ask questions, etc. even if you feel you are 'bugging them'. As you want answers for your baby---- so keep after them or get a second opinion if you are unhappy with current situation.
I WILL tell you that my first son had what I'd call 'projectile' vomiting as a newborn infant. I went to the doctor about it and they called it spit up. They told me that if I were to pour out a bit of milk on the counter, it would look like tons when it was actually a small amount. I was told to but a little gas X (something sold in the states over the counter for infants who have acid reflux/heartburn, indigestion, etc.) either in the corner of his mouth after feeding or in his bottle when I gave him a bottle. It got better. But that is just my story and I can not advise you really as you have worked with doctors and that is where you need to get info from. All the best and please let me know how it goes, okay?