It sounds to me that you possibly are eating too much at once and you might not be eating slow enough and chewing well enough before you swallow. Also tiny bites goes down easier than large bites. What I used to do is I would make up a bunch of foods that are allowed in the fridge.. such as egg salad, tuna salad, hard boiled egg, meat loaf, sweet potato, macaroni and cheese, chicken, beef, and pork cooked long and slow and tender, then cut super thin and in tiny pieces. After you do all this cooking you can divide it up into small containers and freeze most of it and just take out what you will be eating every few days. Then when you just start to get hungry take a spoonful or two of something you made and heat it up in the microwave for a few seconds and that way you wont get ravenously hungry. Keep in mind foods like potatoes and macaroni and cheese need to be eaten in very small portions, like I used to get maybe 12 portions out of a small potato. Your new tummy is tiny, you dont need to eat much to fill it up. I think maybe you just need to eat more often but in tiny amounts. Also try applesauce and cottage cheese because they are easy to digest. I used to like to mix them together because the applesauce made the cottage cheese sweet. Stay away from bread because bread will tend to make you gag and throw up. However I was allowed 2 crackers per meal which is good to put tuna or egg salad on.
Good Luck..
P.S. if you keep throwing up after trying to eat more often and tiny amounts then you need to call your surgeon because something is wrong.