I used to have a really sensitive stomach, then my doctor put me on a "bland diet"
It really helped and it takes out all the acidic stuff. Pretty much nothing too rough on your sensitive tummy, like salty, spicy, alcoholic, caffeinated, etc. After a while it really helped my stomach catch up with my body and now I can eat almost whatever (though I still can't have hot wings without feeling it later. :[ )
You need to eat more dark green veggies and make sure you are drinking water. You also could just be developing a food allergy. Log your foods that make you sick and talk to your doctor.
Heartburn is normal. Throwing up isnt.
I have u. colitis so pretty much anything I eat bothers my stomach. I have found that fish oil, flax seeds and probiotics have helped me. I still get really bloated every time I eat, but the cramping has minimized.
Eat clean. If you still have the problems log what you eat and when you have the problem so you can see what is causing it.
See a gastroenterologist to see what is going on.
The only other thing would be an eating disorder. I don't know you so I don't know if that could be or not. I had an ED when I was young and I did eventually have vomitting after every meal and sometimes even one bite would start vomitting. So, if that is the case, get help.
In any case see a doctor and be honest about what you are eating and what is going on. Keep a journal of when you have the episodes and see how that lines up with what you are eating at that time (write everything down). Make a doctor appointment now.
If it is GIRD, that would not be a lot of stuff coming up in your mouth. Vomitting is more violent and although it can come up as a surprise you have a little warning (about enough to get to a trash can or toilet). Vomitting is also going to result in emptying more of the contents of your stomach than GIRD will if it comes up into your mouth. Most of the time reflux does not come all the way up and you will feel nothing except maybe heartburn, but some don't feel that until they have erosions.
Sorry for the gross post (tee hee). Good luck and see a doctor. Eating clean will hopefully help.
Maybe you are allergic to healthy food (just kidding). Maybe it is stress? See your doctor, I'd see gastroenterologist if it were me.