I'm really confused and concerned:/

Jake, I feel for you man. I was in a similar position six months ago where I went from a bit of reflux to the pain/pressure problem in your stomach and loss of appetite. The PPI made things much worse for me (Omeprazole), hopefully it works for you. What I think happend to me is that I got SIBO (Small Intestinal Bacteria Overgrowth). Basically I was eating the wrong foods (lots of fiber, sweet potatoes, rice, cereal) that was causing a lot of gas. The gas in turn caused reflux, and bloating. I think that pain/pressure thing you describe is bloating or trapped gas. I'm fixing mine with diet and getting less and less symptoms per day. I'm doing this by eating lean meat, less carbs/sugar/beans/grains/fruit/starchy food, and more leafy greens like kale, spinach as well as eggs, full fat yogurt, cheese and coconut oil. I got the idea from something called the fast tract diet. If you google it, you will find info on it, and all sorts of info, it's by a guy named Dr. Norm.... There is also the Kaufman diet. Look at both and see if one or the other makes sense to you. I started off on the Kaufman diet, and after 3 months noticed improvement, but switching to the fast tract diet, I'm getting better improvement.

I went through the wringer, and I hope the same doesn't happen to you. When I lost my appetite, I could only get in 600 calories a day for about 8 weeks. With the SIBO, I wasn't digesting my food either, so I started to get bad anxiety, and charlie horses from not being able to absorb vitamin b12 and magnesium. It took me three months to see gains in improvement after two months starving to death as I couldn't get food in me from that pressure pain feeling you mention. The pressure/pain feeling left me recently.

The coughing and shortness of breath is acid reflux, as it's acid fumes getting into your lungs. (That's one explanation, and it's common, I certainly had it, as well as waking up choking on acid). It can't kill you, but can lead to asthma and pneumonia.

Obviously I'm not a doctor, nor do I play one on TV, but you should see a GI specialist or and ENT to check you out for ulcers, or H Pyloiri, or something sinister to put you at ease. I doubt you do, but if you starve for much longer, your anxiety is going to go off the rails. At your age, your family is probably going to be worried sick about you if you aren't eating. Maybe they'll help cover your costs.

Also, try to do some light exercise, despite your weakness, and lack of calories. Walk around the block or something... Do this as moving helps you digest your food better, and it helps get the gas out of you through burping, rather than refluxing. I stopped exercising as I was so worried about my weight loss... it was a huge mistake.

You'll get better, check out the Fast Tract Diet, or Dropping Acid Diet, see if those make sense, if not, ask more questions on here, and hopefully someone has better advice than me that will help you out.